Hi how to solve this question 3n-5;where n=-1​

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?

What is the number 321,000,000 in scientific notation? also what is the number? ?

Which number line represents the solution set for the inequality - x 24?