7y + 13 - 4z
We have y=5 and z =9.
Everything you need to do is replace y by it's value, and z by it's value, and calculate following the orders of operations.
7*5 + 13 - 4*9
First, you calculate the multiplications, then you subtract and add.
35 + 13 - 36 = -1 + 13 = 12
Hope this Helps! :)