I assume by "x -2" is on the rectangle you mean the length of the rectangle is x - 2. So If I understand the question correctly, then:
P = 2L + 2H
44 = 2(2 +x) + 2(6)
44 = 4 + 2x + 12
44 - 16 = 2x
28...

Yes. A slope does exist. Slope is just "Rise over run".
(y1 - y2) / (x1 - x2) = m
This can also be expressed as: m = Δy / Δx (slope equals Delta y over Delta x [Delta is commonly used to represent "the change in".])
So... plug in the...

Perimeter = Sum of the length of the sides.
Sense we're dealing with a square, all sides are equal. Therefore, the perimeter of the square would be:
4 + 4 + 4 + 4 = 4 * 4 = 16.
16 cm.

If I understand the question correctly - you're looking for a formula to express a graph going through the listed points.
Okay... if you plot this on a graph it looks to have a slope of 1/1 (that is, for every one it moves over via 'x' , it moves up one. When x = 0, y = 7, so we know we have...

(5-z)/z = 9
Multiply both sides by "z".
(5-z)/z*z = 9z
5-z = 9z
Put the variable on one side.
10z = 5
z = .5
Do I need to break it down further?

l=3w-2
l*w=21
(3w-2)*w=21
3w2-2w=21
3w2-2w-21=0
We can now apply the quadratic formula:
(-b +/- SQRT(b2 - 4ac))/2a
plug in the values:
(-(-2) + SQRT((-2)2 - 4(3)(-21))/2(3)
(2 + SQRT(4 + 252))/6 = x
(2 + 16)/6 = x
18/6 = 3
x = 3
w...

Sounds like a volume problem to me. Calculate the total volume of the patio. Convert units.
V = L x W x H
123in3 = 1 ft3
33ft3 = 1 yd3