Justin is older than Martina. The difference in their ages is 22 and the sum of their ages is 54. What age is Martina?

Assumptions and givens:

Let Justin's age be j

Let Martina's age be m

j > m (since Justin is older than Martina)

We're given the following equations :

j - m = 22

j + m = 54

Since the coefficients of m are opposites, we can take a shortcut using the elimination method and add equation (1) to equation (2)
(j + j) + (m - m) = 22 + 54
2j = 76