Question 855715
Son's age = s1 & s2
father's age =f

(s1+s2+f)/3 = 20

s1+s2+f=60

(s1+s2)/2=10

s1+s2=20

.....
s1+s2+f=60

20+f=60
f=60-20
f=40

Father's age=40 years