5/8

3/4

\(a)\dfrac{3}{4}.\dfrac{5}{6}=\dfrac{5}{8}\)

\(b)\dfrac{2}{7}:\dfrac{4}{9}=\dfrac{9}{14}\)

\(\dfrac{3}{4}x\dfrac{5}{6}=\dfrac{3x5}{4x6}=\dfrac{15}{24}=\dfrac{5}{8}\)

b) \(\dfrac{2}{7}:\dfrac{4}{9}=\dfrac{2}{7}x\dfrac{9}{4}=\dfrac{18}{28}=\dfrac{9}{14}\)

\(\dfrac{1}{3}+\dfrac{5}{6}\cdot\left(x-\dfrac{11}{5}\right)=\dfrac{3}{4}\)

\(\dfrac{5}{6}\cdot\left(x-\dfrac{11}{5}\right)=\dfrac{3}{4}-\dfrac{1}{3}\)

\(\dfrac{5}{6}\cdot\left(x-\dfrac{11}{5}\right)=\dfrac{5}{12}\)

\(x-\dfrac{11}{5}=\dfrac{5}{12}\cdot\dfrac{6}{5}\)

\(x-\dfrac{11}{5}=\dfrac{1}{2}\)

\(x=\dfrac{1}{2}+\dfrac{11}{5}\)

\(x=\dfrac{27}{10}\)

\(\dfrac{5}{6}\left(x-\dfrac{11}{5}\right)=\dfrac{3}{4}-\dfrac{1}{3}\)

\(\dfrac{5}{6}\left(x-\dfrac{11}{5}\right)=\dfrac{5}{12}\)

\(x-\dfrac{11}{5}=\dfrac{5}{12}:\dfrac{5}{6}\)

\(x-\dfrac{11}{5}=\dfrac{1}{2}\)

\(x=\dfrac{1}{2}+\dfrac{11}{5}=\dfrac{27}{10}\)

`@` `\text {Ans}`

`\downarrow`

\(\dfrac{1}{3}+\dfrac{5}{6}\times\left(x-\dfrac{11}{5}\right)=\dfrac{3}{4}\)

\(\dfrac{5}{6}\times\left(x-\dfrac{11}{5}\right)=\dfrac{3}{4}-\dfrac{1}{3}\)

\(\dfrac{5}{6}\times\left(x-\dfrac{11}{5}\right)=\dfrac{5}{12}\)

\(x-\dfrac{11}{5}=\dfrac{5}{12}\div\dfrac{5}{6}\)

\(x-\dfrac{11}{5}=\dfrac{5}{12}\times\dfrac{6}{5}\)

\(x-\dfrac{11}{5}=\dfrac{6}{12}\)

\(x=\dfrac{6}{12}+\dfrac{11}{5}\)

\(x=\dfrac{27}{10}\)

giúp em vs ạ

= 10/15+21/15- 9/15 

= 31/15 - 9/15

=22/15

\(\dfrac{2}{3}+\dfrac{7}{5}-\dfrac{3}{5}=\dfrac{2}{3}+\dfrac{7-3}{5}=\dfrac{2}{3}+\dfrac{4}{5}=\dfrac{10+12}{15}=\dfrac{22}{15}\)

\(\dfrac{13}{6}+\dfrac{5}{3}-2=\dfrac{13+10}{6}-2=\dfrac{23}{6}-2=\dfrac{23-12}{6}=\dfrac{11}{6}\)

Ta có : \(\frac{\frac{3}{5}+\frac{3}{7}-\frac{1}{3}+\frac{3}{11}}{\frac{6}{5}+\frac{6}{7}-\frac{2}{3}+\frac{6}{11}}=\frac{\frac{3}{5}+\frac{3}{7}-\frac{1}{3}+\frac{3}{11}}{2\left(\frac{3}{5}+\frac{3}{7}-\frac{1}{3}+\frac{3}{11}\right)}=\frac{1}{2}\)

Lại có : \(\frac{\left(\frac{1}{4}-\frac{1}{5}-\frac{1}{20}\right).2021}{\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}}=\frac{0.2021}{\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}}=0\)

Khi đó \(B=\frac{1}{2}+0=\frac{1}{2}\)

1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 + ... + 21 - 22 - 23 + 24 + 25.

=(1 - 2 - 3 + 4) + (5 - 6 - 7 + 8) + ......+ ( 21 - 22 - 23 + 24)+25

= 0+0+0+......+0+25

=0+25

=25

~HT~

@Jennie

mk nghĩ ko cần giải thik đâu

vì mk ghép các cặp lại để ra kq bằng 0

sau đó cộng thêm 25

là ra kq 25

~HT

#Jennie

a, \(\frac{3}{10}+\frac{5}{8}=\frac{24}{80}+\frac{50}{80}=\frac{74}{80}=\frac{37}{40}\)

b, \(\frac{1}{8}+\frac{5}{6}=\frac{3}{24}+\frac{20}{24}=\frac{23}{24}\)

c, \(\frac{1}{3}+\frac{1}{6}+\frac{1}{8}=\frac{8}{24}+\frac{4}{24}+\frac{3}{24}=\frac{15}{24}=\frac{5}{8}\)

#Fox