Hhhhmmmmm...
13.50 for food
2.40 for drink
Since there is a voucher for 1/3 of food,
13.50 multiplied by 1/3 is 4.5 which is the discount
13.50-4.5=9
9 is the final cost for the food.
Add 9 to 2.40 for the drink which results in a total of 11.40
To find the amount charged for service you multiply 11.40 by .15
11.40 × .15 = 1.71
You add 1.71 to 11.40
The total is 13.11
