Something so different from what I taught. I have no idea how to solve this.
NOTE: the exponents behind the z's are suppose to be -2.


Did you notice that the x and z dependence of the first two terms are exactly the same? Combine them. If you were told "put the answers in descending order with regard to the x variable", since all three terms have, they can be in any order
x- 3x= -2x.![]()
So use "z^{-2}".NOTE: the exponents behind the z's are suppose to be -2.