Question 847869
a) let be the no of years taken to triple the age of his son.
then father's age = 42+x , son's age = 10+x.
42+x = 3(10+x)
42 + x = 30 + 3x
12 = 2x 
x = 6 

b) Let x be the number of years. father's age = 42+x , son's age = 10+x, daughter's age = 16+x 
42+x = 10+x + 16+ x
x=16