To answer this item, we combine all terms involving the variable z to only one side of the equation. All else will be placed on the other side of the equation. This is as follows,
-cz + 6z = tz + 83
Transposing,
-cz - tz + 6z = 83
Factoring z out,
z(-c - t + 6) = 83
Dividing the equation such that z will be left on one side of the equation,
z = 83 / (-c - t + 6)