This past summer you were hired to work at a custom t-shirt. when a customer place an order for a special design, custom t-shirt charge a one-time fee to set up the design, plus a dee for each t-shirt printed. a customer purchased 2 t-shirt and paid $31 doller. and another customer purchased 5 t-shirt and paid $55. find the cost of the one-time fee for the t-shirt design. be sure to define your variables and check your work!

what method did you use? why?