ok so first we need to get the variable on a different side than the constants. We can add 5 to both sides and get Z/5 = 8 1/4. Just because it easier to deal with, i like to turn a mixed number into an improper fraction so 8 1/4 becomes 33/4.
now we have Z/5 = 33/4
then multiply each side by 5 to get z alone
so we get z = 165/4
also can be written as
z = 41 1/4