john is 10 years older than his brother roberto. The sum of their ages is 32 what is johns age

Question

Substitute method

Answer 1

Let j be john's age and r be Roberto's age :   j + r = 32

 

John is 10 years older than Roberto, so j = r + 10

 

Since you know j = r + 10, substitute (r + 10) for j in the equation j + r = 32

(r + 10) + r = 32

 

Now solve for r, and then once you have r, which is Roberto's age, find John's age.