Explanation:
Let Peter's present age be "p" and his father's age be "x"
So, p = x-24 ;
5 years from now,
Peter's age will be (x-24) + 5 = x-19
His father's age will be x+5.
It is given that 3(x-19)= x+5.
3x - 57 = x + 5 => 2x = 62.
On solving, his father's present age (x) is 31.
So Peter's present age is (p) is x - 24 = 31 - 24 = 7.
Now going in the reverse oder to check the answer.
Peter's present is 7.
5 years from now, it will be 12.
His father's age is 31.
5 years from now, his age will be 36 (which is 3x12).
Hence , the answer to the given problem is 7