Hitesh is 40 years old and Ronnie is 60 years old. How many years ago was the ratio of their ages 3 : 5

\par Suppose, the ratio was 3 : 5, x years ago.

\frac{40 - x}{60 - x} = \frac{3}{5}

5(40 - x) = 3(60 - x)

2x = 20
x = 10