The expression given (27x^2)z/(-3x^2)(z^6), can be simplify as below:
By properties of powers, if you have the same base, you can substract the exponents. Then:
=(27x^2)z/(-3x^2)(z^6)
=-9z/z^6 (As you can see: x^2-2= x^0=1)
=-9/z^5 (Then, z^6-1=z^5)
Therefore, the answer is: The exponent on the variable z is 5.