Find n(AUB)

n(AUB) = 2
n(AUB) = 6
n(AUB) = 4

Problem fathi wants to print out a pdf document that is 48 pages long. to save paper, he decides to print on both sides of each sheet and to print two pages on each side of the sheet. how many sheets of paper will he need?

How do you use the elimination method for this question? explain, because i really want to understand!

How do you solving the solution of each system using elimination?