Thank you for the opportunity to help you with your question!
This question is asking you to multiply out a set of brackets. We use the concept of FOILing, which stands for: FIRSTs OUTERs INNERs and LASTs. The acronym just helps you to make sure you haven't forgotten to multiply any of them.
With that, let's begin!
The "firsts" in this case are z and z, multiplied together to get: z^2
The "outers" in this case are z and -9, which multiply together to make -9z
The "inners" in this case are 7 and z, which multiply together to make 7z
and the "lasts" in this case are 7 and 9, which multiply together to make 63
When we put this all together we get: z^2 - 9z +7z +63
We then look to see if there are any like-terms that we can combine further. In our case, -9z and 7z can be combined into -2z
This gives us a final answer of z^2 -2z +63
Please let me know if you need any clarification. I'm always happy to answer your questions!