Question 29374
if you wanted the values for C(x) and R(x) to equal the same, then you would combine

R(x)=12,000x
C(x)=(-1)9000x + (-1)45,000 --multiply by (-1) and (-1) to get 1 on one side
C(x)=-9,000x-45,000
3,000x-45,000=0 --combine
3000x=45000 --add 45000
x=15 --divide by 3000