Question

A father is $3$ times as old as his son. After $15$ years, he will be twice as old as his son . What are their son age.

Answer 1

Let the present age of son be $x$ years

Then, present age of other $=3x$ years

After $15$ years :

Son's age $=(x+15)$ years

Father's age $=(3x+15)$ years

But, according to the question.

$\Rightarrow (3x+15)=2(x+15)$

$\Rightarrow 3x+15=2x+30$

$\Rightarrow 3x-2x=30-15$

$\Rightarrow x=15$

$\therefore$ Son's age is $15$ years.