Look just at the pattern of the numbers on the right side of the “=” sign as they relate to each other. Just because numbers are used in a sequencing problem doesn’t make it a valid math problem. The “=” sign was not correct in any of the equations.
The = sign was used in its usual sense, once you realize that the + sign was used in a generalized sense.
How about this one?
2 + 3 = 1
7 + 2 = 5
6 + 5 = 3
8 + 4 = 12
9 + 7 = ?????
Here, the + sign has the meaning it holds in a widely practiced mathematical usage.