Answer:
10
Step-by-step explanation:
Ok, so if you make an equation for the cost of caterer A, you get 15x + 100 = y, with x as the people catered and y as the total cost. For caterer B you get 20x + 50 = y. If we want to see when y is the same, we can substitute the equations to be equal. This gives us 15x + 100 = 20x + 50, or 50 = 5x, or x = 10. This means the cost will be the same with 10 people.