Question

A store charges their customers based on the number of items that they buy. Jane bought four items and was charged $15 and George bought twelve items and was charged $39. Write a function to model the cost based on the number of items you buy. Then determine how much you are charged if you purchase 22 items.

Answer 1

Okay. So why don't we set up some equations, since the answer doesn't seem readily apparent.

Answer 2

Let's let x = the cost per item

Answer 3

So 15 = x(12) since jane bought 4 items.

Answer 4

Oh wait, 15 = x(4) my bad

Answer 5

and 39 = x(12)

Answer 6

So, if we divide these out we find that the two do not yield the same result.

Answer 7

So there must be some added cost, y.

Answer 8

So we set up the equations to be
15 = 4x + y
39 = 12x+y

Answer 9

There you can either do substitution, or subtraction. I'm not sure which your teacher taught you?

Answer 10

the answer is 10