a) x + $\frac{1}{4}$ = $\frac{3}{5}$ - ( -$\frac{1}{4}$ )
x + $\frac{1}{4}$ = $\frac{17}{20}$
x = $\frac{17}{20}$ - $\frac{1}{4}$
x = $\frac{3}{5}$
b) $\frac{4}{7}$ - x = $\frac{3}{4}$ - ( - $\frac{2}{5}$ )
$\frac{4}{7}$ - x = $\frac{23}{20}$
x = $\frac{4}{7}$ - $\frac{23}{20}$
x = - $\frac{81}{140}$