This is simple :)
If 9 chairs can fit in one box, and you have 3,456 chairs, just divide how many chairs you have by how many can fit in the box in order to find how many boxes you will need.
3,456/9 = 384
384 boxes will be needed
Make them both equal to y
y=-2x+6
2y=x+6 y=1/2x+3
These are perpendicular since ones slope is -2 and the other is the opposite, 1/2.
0 right? It's not changing at all.