Tìm x biết 7/15 + (5/3 - x) = 9/10

* Hướng dẫn giải

$\begin{array}{l}\frac{7}{15}+\left(\frac{5}{3}-\mathrm{x}\right)=\frac{9}{10}\\ \frac{5}{3}-\mathrm{x}=\frac{9}{10}-\frac{7}{15}=\frac{13}{30}\\ \mathrm{x}=\frac{5}{3}-\frac{13}{30}=\frac{37}{30}.\end{array}$