Tìm x ?

* Hướng dẫn giải

a,  $$\begin{gathered} x+ \frac{1}{4}=\frac{5}{8} \\ x=\frac{5}{8}-\frac{1}{4} \\ x=\frac{5}{8}-\frac{2}{8} \\ x=\frac{3}{8} \end{gathered}$$                               b, $$\begin{gathered} \frac{3}{5}-x=\frac{3}{8} \\ x=\frac{3}{5}-\frac{3}{8} \\ x=\frac{24}{40}-\frac{15}{40} \\ x=\frac{9}{40} \end{gathered}$$