A father is twice as old as his son and the sum of their ages is 75. How old is the
father?

50

Let's first of all assume the son's age as x.

So,

Father's age will be 2x i.e. twice as old as the son

Given that,

Sum of their ages = 75 years

So,

x + 2x = 75

3x = 75

x = 75/3

x = 25

Hence,

Son's age = x = 25 years

Father's age = 2x = 2 * 25 = 50 years