The ratio of present ages of father and son is $7:2$, and after $5$ years it becomes $8:3$. Father's present age is—

Let the ages be $7x$ and $2x$; after $5$ years, $\dfrac{7x+5}{2x+5}=\dfrac{8}{3}$ gives $21x+15=16x+40$, so $x=5$. Therefore the father's present age is $7x=35$ years.