I don’t understand any of it because my teacher didn’t teach me

Can someone explain the elimination method to me for this problem?

Saline iv fluid bags cost $64.20 for 24, 1000 ml bags from one supplier. another supplier sells 500 ml bags for $2 each. the hospital uses about 10,000, 1000 ml bags each month. nurses report that about half of the bags are more than half full when they are discarded. if you are going to use only one supplier, which would you choose and how much would you save with that choice? show calculator try it! if you buy 1000 ml bags, how many do you need to buy each month? type your answer in the space provided and click on the check answer button.

Which of the following statements is not true? a. parallel lines are lines in the same plane that never intersect. b. congruent figures have the same shape and same size angles and sides. c. similar figures must have the same shape and the same size. d. a rotation is when you turn a figure around a certain point.