5 times.
1a + 7b + 9a = 10a + 7b
2a + 7b + 8a = 10a + 7b
3a + 7b + 7a = 10a + 7b
4a + 7b + 6a = 10a + 7b
5a + 7b + 5a = 10a + 7b
9.4m questions
12.2m answers