Answer:
The answer is 5
Explanation:
In the fist equation, we can agree that a = 2, since 9 - 7 equals a which at the same time it does with 2.
So, we can substitute a by 2 and the answer would be something like this:
a + 8 = b + 5
2 + 8 = b + 5
10 = b + 5
5 = b