To solve this we just need to understand that when A=1, B=7. So when the side for a is 7 that is basically multiplying A by 7 so we have to do the same to the B side. So when the B side is multiplied by 7 it would be 7*7 =49 so the ? is equal to 49 when that similar side is equal to 7.
This is all based on the fact that the two triangles must be similar triangles.
