Help, this is hard, 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?

45% of the trees in a park are apple trees. there are 27 apple trees in the park. how many trees are in the park in all?

Me find the value of x each figure.