Solve equations using addition x+y=5 and x-y=3

If f(x)= 3x+6 which of the following is the inverse of f(x)

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?

The parabola x= √y-9 opens: a.)up b.)down c.)right d.)left