Question 836765
Hello!

First, let: x be the present age of Mohan.

From the statement: "Mohan's mother is 20 years older than him." = (x + 20); therefore Mohan's mother's age will be: "(x + 20)"

"ten years ago,she was three times as old as mohan was then..."

(x + 20) - 10 = (3)(x - 10)

solve for x.

and x = 20. 

Mohan = 20 years old.
Mother = 40 years old.