Elle ordered some large pizzas and some medium pizzas for a party. in all, she ordered 18 pizzas. large pizzas cost $14, and medium pizzas cost $10. in all, she spent $204. determine if each equation is a part of the system of equations that can be used to find the number of each type of pizza that was ordered. the variable x represents the number of large pizzas, and y represents the number of medium pizzas.