A man's age is three times that of his son and in twelve years he will be twice as old as his son would be. Find their present ages.

The correct answer is: D Present age of man is 36 years and
Present age of son is 12 years

Here we have to find that age of man and his son,
Firstly , it is given at first the man age is three times his son .
Lets father be a and son be b,
So , b = 3a ---(1)
And after twelve years ,
man age is twice age to his son , so we can write,
b+12 = 2(a+12) [we add 12 in both sides because it is after 12 years so both age ages are added by 12]
b + 12 = 2a + 24
3a + 12 = 2a + 24( using (1))
3a – 2a = 24 - 12
a =12
put value of a in eq (1),
b = 3a
b = 3 x 12
b = 36
Therefore , The present age of man and his son is 12 and 36
The correct answer is Present age of man is 36 years and Present age of son is 12 years.
Or,
Let the present age of son be x years
As per question the present age of father is three times
then present age of father is 3x
As per question after 12 years the age of father will be twice the age of son
3x+12=2(x+12)
⇒3x+12=2x+24
⇒3x−2x=24−12
⇒x=12
Then present age of son is 12 years
So present age of father =3×12=36 years

In this question, we have to make equation on the given date about ages. Consider all the character in similar ages question be some variable and make the equation on given details.