Answer:
G=39, F=141
Step-by-step explanation:
Let us set up equations, with G and F as variables.
Since G and F are supplementary, they must add up to 180.
G+F=180
Given the equation, we can set it up too
F = 4 * G - 15
Here, we can solve for this equation by plugging the second equation into the first one with substitution
G+4*G-15=180
simplify and solve
5G=195
G=39
Plug this into the first equation to solve for F:
39+F=180
F=141
We can plug both answers into the second equation to check and find that we are indeed right.