Question

Riley is 3 years older than his sister. Which of the following expressions shows the sum of their ages if s represents Riley's sister's age?

Answer 1

If s is Riley's sister's age, their sum is s+(s+3), or 2s+3.

Answer 2

2s + 3

Explanation:

If we name s Riley's sister's age, the problem tells us that Riley is 3 years older than her so his age would be s + 3

Thus, the sum of their ages would be:

Riley's age + Riley's sister's age

(s + 3) + s = s + 3 + s = 2s + 3

Thus, the expression would be 2s + 3