For this, combine like terms. In this case, the like terms are 3x-2x, 2y+3y, and (-5). Combine them, and your answer will be 
Omit means: "to leave out" or "not include"
the area of the cuboid is 560
the perimeter of the cuboid is 2240
I think if they were asking you for the remainder in 35 ÷ 4 it would be 3
No the 6 times 8 is 48 and the 9 times 12 is 108