If a = 3y + 4z and b = z - 2y, then what is the value of a + b?

7x+8y=-18, 4x-9y=-3 solve the system of equations

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?

Ineed me i stuck and i don’t want to get it wrong