Question

1/Tính:
\(\left(2-\frac{1}{5}\right).\left(\frac{-3}{15}+\frac{1}{3}\right)\)

2/Tìm x, biết:
\(\frac{x}{20}-\frac{2}{5}=\frac{4}{15}.\frac{-9}{8}\)

Answer 1

1.

\(\left(2-\frac{1}{5}\right)\cdot\left(\frac{-3}{15}+\frac{1}{3}\right)\)

\(=\left(\frac{10}{5}-\frac{1}{5}\right)\cdot\left(\frac{-3}{15}+\frac{5}{15}\right)\)

\(=\frac{9}{5}\cdot\frac{2}{15}=\frac{18}{75}\)

Answer 2

2.

\(\frac{x}{20}-\frac{2}{5}=\frac{4}{15}\cdot\frac{-9}{8}\)

\(\frac{x}{20}-\frac{2}{5}=\frac{-9}{30}\)

\(\frac{x}{20}=\frac{-9}{30}+\frac{2}{5}\)

\(\frac{x}{20}=\frac{-9}{30}+\frac{12}{30}\)

\(\frac{x}{20}=\frac{1}{10}\)

\(\frac{x}{20}=\frac{2}{20}\)

\(\Rightarrow x=2\)

Vậy x = 2