Print-o-rama charges a set-up fee and a fixed amount for each shirt ordered. 10 shirts cost $95 and 50 shirts cost $375. How much is the set-up fee

Question

I know the answer, I just don't understand how you can get the set up fee when the table is not proportionate.

Answer 1

Set up linear equations y = mx + b with m the slope, the per shirt fee. b is the y intercept, the setup fee, starting cost.

call x the number of shirts, and y the total price.

95 = 10x + b

375 = 50x + b

Subtract the first equation from the second.

280 = 40x

280/40 = x = 7 per shirt.

95 = 10*7 + b

95 = 70 + b

25 = b