Tìm x biết: 2/3.x + 1/2 = 1/10

Hướng dẫn giải:

Đáp án đúng là: B

\(\frac{2}{3}.x + \frac{1}{2} = \frac{1}{{10}}\)

\(\frac{2}{3}.x = \frac{1}{{10}} - \frac{1}{2}\)

\(\frac{2}{3}.x = \frac{1}{{10}} - \frac{5}{{10}}\)

\(\frac{2}{3}.x = \frac{{ - 4}}{{10}}\)

\(\frac{2}{3}.x = \frac{{ - 2}}{5}\)

\(x = \frac{{ - 2}}{5}:\frac{2}{3}\)

\(x = \frac{{ - 2}}{5}.\frac{3}{2}\)

\(x = \frac{{ - 3}}{5}\)

Vậy \(x = \frac{{ - 3}}{5}\)