plz help i need answer.

Answer:
C
Step-by-step explanation:
Make a system of equations.
Justin = j
Greg = g
j + 15 = g
g/2 + 75 = j
We can substitute.
(j + 15)/2 + 75 = j
j/2 + 15/2 + 75 = j
j/2 = 165/2
j = 165
Substitute back into j + 15 = g
165 + 15 = g
g = 180