Need help getting the answer to this question

Question

Jack is three years older than Jill. The sum of their ages is greater than 19. Describe Jill’s age.

Answer 1

Jack is three years older than Jill means Jack=3+Jill

The sum of their ages is greater than 19 means Jack + Jill>19 but since we know that Jack=3+Jill we have that 3+Jill+Jill>19

3+Jill+Jill>19

2xJill>19-3

2xJill>16

Jill>8