Let, Father's age = F Elder son's age = E Yonger son's age = Y
From question,
Father is twice of elder son, F = 2E -----> (1)
Difference between elder and younger son, E - Y = 15 Therefore, Y = E - 15 -----> (2)
After 10 years, father's age is thrice the age of younger son, F + 10 = 3( Y + 10 ) -----> (3)
Substitute (1) and (2) in (3)
2E + 10 = 3 ( {E - 15} + 10 ) Solving, E = 25
Therefore, F = 2E = 2 * 25 = 50
50