a.x + 2/5 = 1 - 1/6

x + 2/5 = 5/6

x= 13/30

b.3/4 - 2/5 + 5/12

=7/20 + 5/12

=23/30

a)\(x=\left(1-\dfrac{1}{6}\right)-\dfrac{2}{5}=\dfrac{5}{6}-\dfrac{2}{5}=\dfrac{13}{30}\)

b)\(=\dfrac{7}{20}+\dfrac{5}{12}=\dfrac{23}{30}\)

a.x + 2/5 = 1 - 1/6

x + 2/5 = 5/6

x= 13/30

b.3/4 - 2/5 + 5/12

=7/20 + 5/12

=23/30

a) 10/7 - 3/8 

= 59/56

b) 9/10- 7/12

= 19/60

giúp mình với

a 4/7 x 5/2 -3/8 = 10/7 - 3/8 = 59/56

b 9/10 - 7/12 =19/60

a) \(\dfrac{5}{4}+\dfrac{3}{5}=\dfrac{25}{20}+\dfrac{12}{20}=\dfrac{37}{20}\)

b) \(\dfrac{7}{8}+\dfrac{9}{24}=\dfrac{21}{24}+\dfrac{9}{24}=\dfrac{30}{24}=\dfrac{15}{12}\)

c) \(\dfrac{2}{36}+\dfrac{1}{6}+\dfrac{5}{12}=\dfrac{2}{36}+\dfrac{6}{36}+\dfrac{15}{36}=\dfrac{23}{36}\)

a) \(\dfrac{5}{4}+\dfrac{3}{5}=\dfrac{25}{20}+\dfrac{12}{20}=\dfrac{37}{20}\)

b) \(\dfrac{7}{8}+\dfrac{9}{24}=\dfrac{21}{24}+\dfrac{9}{24}=\dfrac{30}{24}=\dfrac{5}{4}\)

c) \(\dfrac{2}{36}+\dfrac{1}{6}+\dfrac{5}{12}=\dfrac{2}{36}+\dfrac{6}{36}+\dfrac{15}{36}=\dfrac{23}{36}\)

Áp dụng dãy tỉ số bằng nhau:

b.

\(\dfrac{x}{2}=\dfrac{y}{-5}=\dfrac{x-y}{2-\left(-5\right)}=\dfrac{-7}{7}=-1\)

\(\Rightarrow\left\{{}\begin{matrix}x=2.\left(-1\right)=-2\\y=-5.\left(-1\right)=5\end{matrix}\right.\)

d.

\(\dfrac{4}{x}=\dfrac{7}{y}\Rightarrow\dfrac{y}{7}=\dfrac{x}{4}=\dfrac{y-x}{7-4}=\dfrac{-12}{3}=-4\)

\(\Rightarrow\left\{{}\begin{matrix}x=4.\left(-4\right)=-16\\y=7.\left(-4\right)=-28\end{matrix}\right.\)

a, 7\(\dfrac{3}{5}\) : \(x\) = 5\(\dfrac{4}{15}\) - 1\(\dfrac{1}{6}\)

     \(\dfrac{38}{5}\) : \(x\) = \(\dfrac{79}{15}\) - \(\dfrac{7}{6}\)

              \(x\) = \(\dfrac{41}{10}\)

             \(x\) = \(\dfrac{38}{5}\) : \(\dfrac{41}{10}\)

              \(x\) = \(\dfrac{76}{41}\)

b, \(x\) \(\times\) 2\(\dfrac{2}{3}\) = 3\(\dfrac{4}{8}\) + 6\(\dfrac{5}{12}\)

    \(x\) \(\times\) \(\dfrac{8}{3}\)  = \(\dfrac{7}{2}\) + \(\dfrac{77}{12}\)

     \(x\) \(\times\) \(\dfrac{8}{3}\) = \(\dfrac{119}{12}\)

     \(x\)          = \(\dfrac{119}{12}\)

     \(x\)          = \(\dfrac{119}{12}\): \(\dfrac{8}{3}\)

     \(x\)           = \(\dfrac{119}{32}\)

a. \(=\left(\dfrac{12}{15}+\dfrac{3}{15}\right)+\left(\dfrac{4}{3}+\dfrac{5}{3}\right)+\left(\dfrac{1}{4}+\dfrac{3}{4}\right)\\ =1+2+1=4\)

b. \(x\times\dfrac{3}{4}=\dfrac{1\times3\times6\times5}{6\times5\times5\times3}\\ x\times\dfrac{3}{4}=\dfrac{1}{5}\\ x=\dfrac{1}{5}:\dfrac{3}{4}\\ x=\dfrac{4}{15}\)

a.

(12/15+3/15)+(4/3+5/3)+(1/4+3/4)

=1+3+1=5

b.X x 3/4=1/5

           X=1/5:3/4

           X=4/15

a) \(\dfrac{13}{20}+\dfrac{3}{5}+x=\dfrac{5}{6}\)

\(\Rightarrow\dfrac{5}{4}+x=\dfrac{5}{6}\)

\(\Rightarrow x=\dfrac{5}{6}-\dfrac{5}{4}\)

\(\Rightarrow x=\dfrac{-5}{12}\)

b) \(x+\dfrac{1}{3}=\dfrac{2}{5}-\dfrac{-1}{3}\)

\(\Rightarrow x+\dfrac{1}{3}=\dfrac{11}{15}\)

\(\Rightarrow x=\dfrac{11}{15}-\dfrac{1}{3}\)

\(\Rightarrow x=\dfrac{2}{5}\)

c)\(\dfrac{-5}{8}-x=\dfrac{-3}{20}-\dfrac{-1}{6}\)

\(\dfrac{-5}{8}-x=\dfrac{1}{60}\)

\(\Rightarrow x=\dfrac{-5}{8}-\dfrac{1}{60}\)

\(\Rightarrow x=\dfrac{-77}{120}\)

d) \(\dfrac{3}{5}-x=\dfrac{1}{4}+\dfrac{7}{10}\)

\(\Rightarrow\dfrac{3}{5}-x=\dfrac{19}{20}\)

\(\Rightarrow x=\dfrac{3}{5}-\dfrac{19}{20}\)

\(\Rightarrow x=\dfrac{-7}{20}\)

e) \(\dfrac{-3}{7}-x=\dfrac{4}{5}+\dfrac{-2}{3}\)

\(\Rightarrow\dfrac{-3}{7}-x=\dfrac{2}{15}\)

\(\Rightarrow x=\dfrac{-3}{7}-\dfrac{2}{15}\)

\(\Rightarrow x=\dfrac{-59}{105}\)

g) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)

\(\Rightarrow\dfrac{-5}{6}-x=\dfrac{1}{4}\)

\(\Rightarrow x=\dfrac{-5}{6}-\dfrac{1}{4}\)

\(\Rightarrow x=\dfrac{-13}{12}\)

A,-8

B,-36

C,-80

{Mình tính bằng máy tính }

a) x=4/2

b) x=1/12

c) 24/35

a,\(\dfrac{1}{2}+x=\dfrac{5}{2}\)

\(x=\dfrac{5}{2}-\dfrac{1}{2}\)

\(\Rightarrow x=2\)

b,\(\dfrac{3}{4}-x=\dfrac{2}{3}\)

\(x=\dfrac{3}{4}-\dfrac{2}{3}\)

\(\Rightarrow x=\dfrac{1}{12}\)

c,\(x:\dfrac{4}{5}=\dfrac{6}{7}\)

\(x=\dfrac{6}{7}.\dfrac{4}{5}\)

\(\Rightarrow\dfrac{24}{35}\)

a)1/2+x=5/2                                          b)3/4-x=2/3

    x=5/2-1/2=4/2=2                                  x=3/4-2/3=1/12

c)x:4/5=6/7

   x=6/7.4/5=24/35