Answer:
Infinite solutions
Explanation:
Since it is a negative number plus the same number, but positive, it will always be equal to 0, no matter what z is.
If z is 0, it will be 0 + 0 = 0
If z is 1, it will be -5 + 5 = 0
If z is 2, it will be -10 + 10 = 0
If z is 1,000,000, it will be -5,000,000 + 5,000,000 = 0
So this means that there are infinite solutions.
Hope this helps!