$Increment \ value : = $ $\frac{1}{4} \times (0.2x+y)=y \\ y= \frac{0.2x}{3} $

$New \ salary = \frac{0.2x}{3}+0.2x = \frac{0.8x}{3}$

New salary in terms of family income = $\LARGE \frac{\frac{0.8x}{3}}{x+\frac{0.2x}{3}} $$\times 100=25\%$