Question

Three friends split the cost of pizza and a salad. The pizza costs $15 and the salad costs $6.

Answer 1

Each pays $7. 15+6=21 and 21/3=7

Answer 2

Each person would have to pay $7
Split the price of the pizza which is $15, 15 divides by 3 is $5
Then add the $5 per person for the pizza for the cost of the salad divided by 3, $6 divided by three is 2
$2+$5= $7 per person

Or you could add the cost of the pizza and the salad
$15+$6=$21
And divide that by the number of people
$21 divided by three is $7