Tìm x, biết: a) x-( 5/4 -7/5) = 9/20;

* Hướng dẫn giải

a) $x-\left(\frac{5}{4}-\frac{7}{5}\right)=\frac{9}{20}$

$x=\frac{9}{20}+\left(\frac{5}{4}-\frac{7}{5}\right)$

$x=\frac{9}{20}+\frac{5}{4}-\frac{7}{5}$

$x=\frac{9}{20}+\frac{25}{20}-\frac{28}{20}$

$x=\frac{6}{20}$

$x=\frac{3}{10}$

Vậy $x=\frac{3}{10}$