Answer: -7z
Explanation:
1. We can start off by pretending that -8x and 8x are invisible.
2. That would leave us with 8z-15z.
3. We know that 8z-15z equals -7z, so know we have a base to start with.
4. We can add -8x and 8x again, which will give us the equation -7z-8x+8x.
5. This is also equal to -7z
6. The answer is -7z.