To determine how much pizza your friend has left, we first need to know how many pizzas he ordered. He ordered two pizzas, but the problem doesn't specify how many slices each pizza contains.
Assuming each pizza has a total of 16 slices (a common number for many pizza sizes), then:
Total slices from 2 pizzas = 2 pizzas × 16 slices/pizza = 32 slices.
If he gives you 13 slices and another friend 12 slices, we can calculate the total number of slices given away:
Total slices given away = 13 slices + 12 slices = 25 slices.
Now we calculate the slices remaining:
Remaining slices = Total slices - Total slices given away = 32 slices - 25 slices = 7 slices.
Thus, your friend has 7 slices of pizza left.