5. Y=1/2x+12
6. Y=4x+8
7. Y=1/4x+256
Answer:

Step-by-step explanation:
(Given)
Maybe i have that you wanted
We can represent the situation like that:
Y=-15 and x=-20
Then When y=12 x=?
We make x(The unknown) *-15=12*(-20)
We have an simple équation to solve
Thus x=(12*(-20))/-15
X=16