Question

Bobby is 3 years younger than 5 times his grandson's age. The sum of their ages is greater than 75. What is the youngest age Bobby’s grandson can be?

Answer 1

The youngest age Bobby's grandson can be is 16.

Explanation:

1. Use variables

Bobby=B Grandson=G

B=5(G)-3

B+G is greater than 75

2. Use trial and error

If G is 15.. 5(15)-3=72. This does not work

If G is 16... 5(16)-3=77 This works

So his grandson must be at least 16 years old.

Answer 2

If his age was 13 then it would add up to exactly 75, but to be greater it would be 14. I would put a note by the question if I were you.