What is -2 radical 54 (please help)

Giuseppi's pizza had orders for $931.00 of pizzas. the prices were $21 for a large pizza, 514 for a medium pizza, and $7 for a small pizza. the number of large pizzas was two less than four times the number of medium pizzas. thenumber of small pizzas was three more than three times the number of medium pizzas. how many of each size of pizza were ordered?

I'm confused on this could anyone me and show me what i need to do to solve it.

Which steps could be part of the process in algebraically solving the system of equations, y+5x=x^2+10 and y=4x-10