20 points with a step-by-step explanation

Find the sum of the following series. round to the nearest hundredth if necessary.

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?

Ihave trouble finding the nth term of a linear sequence