Đề bài

Tìm x biết: a) \(\frac{7}{{ - 8}} - x = \frac{{ - 4}}{5}:\frac{3}{{10}}\) b) \(\frac{{ - 5}}{6}.x = \frac{{ - 5}}{8} - 1\frac{3}{4}\)

Lời giải chi tiết

a) \(\begin{array}{l}\frac{7}{{ - 8}} - x = \frac{{ - 4}}{5}:\frac{3}{{10}}\\\frac{7}{{ - 8}} - x = \frac{{ - 4}}{5}.\frac{{10}}{3}\\\frac{7}{{ - 8}} - x = \frac{{ - 8}}{3}\\x = \frac{7}{{ - 8}} - \frac{{ - 8}}{3}\\x = \frac{{43}}{{24}}.\end{array}\)b) \(\begin{array}{l}\frac{{ - 5}}{6}.x = \frac{{ - 5}}{8} - 1\frac{3}{4}\\\frac{{ - 5}}{6}.x = \frac{{ - 5}}{8} - \frac{7}{4}\\\frac{{ - 5}}{6}.x = \frac{{ - 19}}{8}\\x = \frac{{ - 19}}{8}:\frac{{ - 5}}{6}\\x = \frac{{57}}{{20}}.\end{array}\)