Answer :
No. Jack's solution doesn't make sense.
Step-by-step explanation:
It is given that, 8.5 - a = 5
Jack is saying that addition and subtraction are the reverse operations. Yes it's true, but here,
8.5 - a = 5
If we move 5 to the opposite side, it becomes -5, and -a to the other side, it becomes a.
So, 8.5 - 5 = 3.5 and not 13.5.
Overall, Jack's solution doesn't make sense.