See the attached picture:
(f-g)(x) = x²+6x - (7-x)
(f-g)(x) = x² + 6x - 7 + x
(f-g)(x) = x² + 7x - 7
(f-g)(9) = 9² + 7*9 - 7
(f-g)(9) = 81 + 63 - 7
(f-g)(9) = 137
N is the number of the Tshirt
c is the cost
the relationship between the cost and the number of the Tshirt is:
12n+3=c
so if 1 is the number of the tshirt so the cost is
12.1+3=12+3=15
if n=2 c=12.2+3=24+3=27
and etc.....
