Because the prices are different, you need to use two variables, one for each price.
Let the price for the plain one be X and the price for the printed one be Y.
You would multiply the number of each shirt by the variable:
3 plain would be 3X and 2 printed would be 2Y.
You then need to add those together to get the total cost:
Total cost = 3X + 2Y
40 flights, you could use rates in this situation.
15 min*4=60 min=1 hr
10:15 multiply each side by 4
40 flights:60 minutes
I think the answer would be 89
