Tìm giá trị của x , biết: (a) x/15 = − 2/5 . (b) 8/5 − 4/5 x = − 1/10 .

a) \(\frac{x}{{15}} = \frac{{ - 2}}{5}\)

\(x = \frac{{ - 2 \cdot 15}}{5}\)

\(x = - 6.\)

Vậy \(x = - 6.\)

b) \(\frac{8}{5} - \frac{4}{5}x = \frac{{ - 1}}{{10}}\)

\(\frac{4}{5}x = \frac{8}{5} - \frac{{ - 1}}{{10}}\)

\(\frac{4}{5}x = \frac{{17}}{{10}}\)

\(x = \frac{{17}}{{10}}:\frac{4}{5}\)

\(x = \frac{{17}}{8}.\)

Vậy \(x = \frac{{17}}{8}.\)