In a pizzeria, you pay $7 for each of the first three
pizzas, and $6 for the following pizzas. how many
pizzas did gerry's band buy, if they paid $45?

7 pizzas.

Step-by-step explanation:

First you figure out how much the first three pizzas cost. 7x3 = 21. They paid $21 for the first 3. Subtract that number from the total cost.

45 - 21 = 24. Since the rest of the pizzas were only 6 dollars, divide the remaining amount by 6.

24/6 = 4. They bought 4 additional pieces. Add the amount of pizzas they bought together.

3 + 4 = 7