This is an inequality problem. The way to solve this is to treat the inequality sign (<, >, etc) like an equal sign (=).
-7z - 7 = -5z + 5
first, you get rid of the constants (the numbers that don't have variables with them) the way to do that is to perform reverse operations (when there is a negative, add. when positive, subtract. same for multiplying and dividing)
The range is the set of all possible output, as you feed the function with all possible inputs. Since our inputs (domain) are -3, 0, 3, our outputs are