Jin (WWH) spends 18.55 for every 7 tacos he gets. That means he spends 18.55÷7 for every taco he gets.
18.55÷7 = 2.65
Now you need to find how much he spends for 15 tacos. If one taco is 2.65, you need to multiply 15 by 2.65 to find the price for 15 tacos.
2.65×15=39.75.
Jin will have to pay $39.75 for 15 tacos.