\(A=\frac{-7}{21}+\left(1+\frac{1}{3}\right)\)

\(A=\frac{-7}{21}+1+\frac{1}{3}\)

\(A=\left(\frac{-7}{21}+\frac{1}{3}\right)+1\)

\(A=0+1\\ A=1\)

\(B=\frac{2}{15}+\left(\frac{5}{9}+-\frac{6}{9}\right)\)

\(B=\frac{2}{15}+\frac{-1}{9}\)

\(B=\frac{1}{45}\)

\(C=\left(\frac{-1}{5}+\frac{3}{12}\right)+\frac{-3}{4}\)

\(C=\frac{-1}{5}+\left(\frac{3}{12}+\frac{-3}{4}\right)\)

\(C=\frac{-1}{5}+\frac{-1}{2}\)

\(C=\frac{-7}{10}\)

\(A=\frac{-7}{21}+\left(1+\frac{1}{3}\right)\)

\(A=\frac{-1}{3}+1+\frac{1}{3}\)

\(A=1\)

\(B=\frac{2}{15}+\left(\frac{5}{9}+\frac{-6}{9}\right)\)

\(B=\frac{2}{15}+\frac{5}{9}+\frac{-6}{9}\)

\(B=\frac{2}{15}+\frac{5}{9}+\frac{-10}{15}\)

\(B=\frac{-8}{15}+\frac{5}{9}\)

\(B=\frac{1}{45}\)

\(C=\left(\frac{-1}{5}+\frac{3}{12}\right)+\frac{-3}{4}\)

\(C=\frac{-1}{5}+\frac{3}{4}+\frac{-3}{4}\)

\(C=\frac{-1}{5}\)

a,\(2-\frac{5}{7}+\frac{9}{21}\)

\(=2-\frac{154}{147}\)

\(=\frac{135}{147}\)

b, \(\frac{5}{8}\):\(3+\frac{25}{24}\)

\(=\frac{5}{24}+\frac{25}{24}\)

\(=\frac{30}{24}\)

`5`

`a, -7/21 +(1+1/3)`

`=-7/21 + ( 3/3 + 1/3)`

`=-7/21+ 4/3`

`=-7/21+ 28/21`

`= 21/21`

`=1`

`b, 2/15 + ( 5/9 + (-6)/9)`

`= 2/15 + (-1/9)`

`= 1/45`

`c, (9-1/5+3/12) +(-3/4)`

`= ( 45/5-1/5 + 3/12)+(-3/4)`

`= ( 44/5 + 3/12)+(-3/4)`

`= 9,05 +(-0,75)`

`=8,3`

`6`

`x+7/8 =13/12`

`=>x= 13/12 -7/8`

`=>x=5/24`

`-------`

`-(-6)/12 -x=9/48`

`=> 6/12 -x=9/48`

`=>x= 6/12-9/48`

`=>x=5/16`

`---------`

`x+4/6 =5/25 -(-7)/15`

`=>x+4/6 =1/5 + 7/15`

`=> x+ 4/6=10/15`

`=>x=10/15 -4/6`

`=>x=0`

`----------`

`x+4/5 = 6/20 -(-7)/3`

`=>x+4/5 = 6/20 +7/3`

`=>x+4/5 = 79/30`

`=>x=79/30 -4/5`

`=>x= 79/30-24/30`

`=>x= 55/30`

`=>x= 11/6`

\(5)\)

\(A=\dfrac{-7}{21}+\left(1+\dfrac{1}{3}\right)\)

\(A=\dfrac{-7}{21}+\dfrac{4}{3}\)

\(A=\dfrac{-7}{21}+\dfrac{28}{21}\)

\(A=1\)

\(--------------\)

\(B=\dfrac{2}{15}+\left(\dfrac{5}{9}+\dfrac{-6}{9}\right)\)

\(B=\dfrac{2}{15}+\dfrac{-1}{9}\)

\(B=\dfrac{18}{135}+\dfrac{-15}{135}\)

\(B=\dfrac{1}{45}\)

\(------------\)

\(C=9-\dfrac{1}{5}+\dfrac{3}{12}+\dfrac{-3}{4}\)

\(C=\dfrac{44}{5}+\dfrac{3}{12}+\dfrac{-3}{4}\)

\(C=\dfrac{528}{60}+\dfrac{15}{60}+\dfrac{-3}{4}\)

\(C=\dfrac{181}{20}+\dfrac{-3}{4}\)

\(C=\dfrac{181}{20}+\dfrac{-15}{20}\)

\(C=\dfrac{83}{10}\)

\(6)\)

\(a)\) \(x+\dfrac{7}{8}=\dfrac{13}{12}\)

\(x=\dfrac{13}{12}-\dfrac{7}{8}\)

\(x=\dfrac{104}{96}-\dfrac{84}{96}\)

\(x=\dfrac{5}{24}\)

\(b)\) \(\dfrac{-6}{12}-x=\dfrac{9}{48}\)

\(\dfrac{-1}{2}-x=\dfrac{3}{16}\)

\(x=\dfrac{-1}{2}-\dfrac{3}{16}\)

\(x=\dfrac{-8}{16}-\dfrac{3}{16}\)

\(x=\dfrac{-11}{16}\)

\(c)\) \(x+\dfrac{4}{6}=\dfrac{5}{25}-\left(-\dfrac{7}{15}\right)\)

\(x+\dfrac{4}{6}=\dfrac{5}{25}+\dfrac{7}{15}\)

\(x+\dfrac{4}{6}=\dfrac{75}{375}+\dfrac{105}{375}\)

\(x+\dfrac{4}{6}=\dfrac{12}{25}\)

\(x=\dfrac{12}{25}-\dfrac{4}{6}\)

\(x=\dfrac{72}{150}-\dfrac{100}{150}\)

\(x=\dfrac{-14}{75}\)

\(d)\) \(x+\dfrac{4}{5}=\dfrac{6}{20}-\left(-\dfrac{7}{3}\right)\)

\(x+\dfrac{4}{5}=\dfrac{6}{20}+\dfrac{7}{3}\)

\(x+\dfrac{4}{5}=\dfrac{18}{60}+\dfrac{140}{60}\)

\(x+\dfrac{4}{5}=\dfrac{79}{30}\)

\(x=\dfrac{79}{30}-\dfrac{4}{5}\)

\(x=\dfrac{79}{30}-\dfrac{24}{30}\)

\(x=\dfrac{11}{6}\)

Giải:

\(A=\dfrac{-7}{21}+\left(1+\dfrac{1}{3}\right)\)

\(A=\dfrac{-7}{21}+\dfrac{4}{3}\)

\(A=\dfrac{-7}{21}+\dfrac{28}{21}\)

\(A=\dfrac{21}{21}=1\)

\(B=\dfrac{2}{15}+\left(\dfrac{5}{9}+\dfrac{-6}{9}\right)\)

\(B=\dfrac{2}{15}+\dfrac{-1}{9}\)

\(B=\dfrac{6}{45}+\dfrac{-5}{45}\)

\(B=\dfrac{1}{45}\)

\(C=\left(9-\dfrac{1}{5}+\dfrac{3}{12}\right)+\dfrac{-3}{4}\)

\(C=\left(\dfrac{44}{5}+\dfrac{1}{4}\right)+\dfrac{-3}{4}\)

\(C=\dfrac{181}{20}+\dfrac{-3}{4}\)

\(C=\dfrac{181}{20}+\dfrac{-15}{20}\)

\(C=\dfrac{166}{20}\)

Bài 6:

\(a)x+\dfrac{7}{8}=\dfrac{13}{12}\)

⇔\(x=\dfrac{13}{12}-\dfrac{7}{8}=\dfrac{5}{24}\)

\(b)\dfrac{-6}{12}-x=\dfrac{9}{48}\)

⇔\(x=\dfrac{-6}{12}-\dfrac{9}{48}=\dfrac{-11}{16}\)

\(c)x+\dfrac{4}{6}=\dfrac{5}{25}-\dfrac{-7}{15}\)

\(\Leftrightarrow x+\dfrac{2}{3}=\dfrac{2}{3}\)

\(\Leftrightarrow x=\dfrac{2}{3}-\dfrac{2}{3}=0\)

\(d)x+\dfrac{4}{5}=\dfrac{6}{20}-\dfrac{-7}{3}\)

⇔\(x+\dfrac{4}{5}=\dfrac{79}{30}\)

⇔\(x=\dfrac{79}{30}-\dfrac{4}{5}=\dfrac{11}{6}\)

Mọi người giúp Mik với, mik cần gấp 

A=10/3

B=1/45

C=-14/20

Hok tốt:)))

Giúp mik giải rõ đc Ko?
 

\(a,\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-\frac{20}{15}+\frac{3}{7}\)

\(=>\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{7}{21}+\frac{3}{7}\right)-\frac{20}{15}\)

\(=>1+\frac{16}{21}-\frac{20}{15}\)

\(=>\frac{37}{21}-\frac{20}{15}\)

\(=>\frac{3}{7}\)

\(b,12-8\cdot\left(\frac{3}{2}\right)^3\)

\(=>12-8\cdot\frac{27}{8}\)

\(=>12-27\)

\(=>-15\)

\(c,\left(\frac{1}{9}\right)^{2005}\cdot9^{2005}-96^2:24^2\)

\(=>\left(\frac{1^{2005}^{ }}{9^{2005}}\cdot9^{2005}\right)-\left(96^2:24^2\right)\)

\(=>\left(1^{2005}\right)-16\)

\(=>1-16\)

\(=>-15\)

21 x 3 : 9 = 63 : 9 = 7

Đáp án: 195

\(A=\frac{9}{15.18}+\frac{9}{18.21}+.....+\frac{9}{89.92}\)

\(A=3.\left(\frac{3}{15.18}+\frac{3}{18.21}+....+\frac{3}{89.92}\right)\)

\(A=3.\left(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+......+\frac{1}{89}-\frac{1}{92}\right)\)

\(A=3.\left(\frac{1}{15}-\frac{1}{92}\right)\)

\(A=3.\frac{77}{1380}=\frac{77}{460}\)

$A=\frac{9}{15.18}+\frac{9}{18.21}+.....+\frac{9}{89.92}$

$A=3.\left(\frac{3}{15.18}+\frac{3}{18.21}+....+\frac{3}{89.92}\right)$

$A=3.\left(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+......+\frac{1}{89}-\frac{1}{92}\right)$

$A=3.\left(\frac{1}{15}-\frac{1}{92}\right)$

$A=3.\frac{77}{1380}=\frac{77}{460}$