Money spent = M
Number of burritos purchased = B
M varies with B, so M is a function of B
M(B)
When B=4 , M= 18
18 = 4 x
x= price per burrito
Solve for x
18/4= x
x = $4.5
So the function is:
M(B) = 4.5 B
If 15 burritos are purchased:
M(15)= 4.5 (15) = $67.5
Answer : $67.5