Question 732880
Let boy's age be b
Let father's age be f


The sum of a boy and his father's age is 63 years
f + b = 63 -----------------------eq. 1


The difference between their ages is 33 years
f - b = 33 -----------------------eq. 2



Solving the 2 equations(Add the 2 equations)
f + b = 63
f - b = 33


2f = 96
f = 96/2 = 48


Father's age is 48 
Substitute f = 48 in eq 1


f + b = 63
48 + b = 63
b = 63 - 48
b = 15


Boy's age is 15
Father's age is 48