Pls help me with this math. its kind of easy...

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?

Find dy/dx using implicit differentiation ln(20+e^xy)=y

Answer for 10 points show work you guys in advanced < 3