Stacy sells homemade pizzas, sizes large and small. a small pizza has 10 olive pieces and 18 mushroom pieces. a large pizza has 15 olive pieces and 45 mushroom pieces. she has enough olives and mushrooms for 60 olive pieces and 135 mushrooms pieces. let x represent the number of small pizzas and y represent the number of large pizzas. write all of the constraints for this situation, and explain each.