A father's age is three times the age of his childs. After five years of age, father's age childs would double the sum, the father's age -

please help me for this question here is not given number of child.

2 answers

f = 3c

f+5 = 2(c+5)

Substitute 3c for f in the second equation and solve for c. Insert that value into the first equation to solve for f. Check by putting both values into the second equation.
age of father 15.age of son 5