Answer: - 6
Explanation:
The only way that you can have infinite solutions is if you try to solve and the answer is something like 1=1, or something that will always be true no matter what.
Solving 5x+(-6)=5x–6:
5x-6=5x–6 /subtract 5x from both sides
-6 = -6
Now we can't solve since there's no x, and -6 = -6 so there are infinite solutions.