For this case we have:
The area of the piece of fabric is given by 
Where


Substituting in the formula of the area we have:




Thus, the area of the piece of fabric is given by: 
Answer:

X = -6y - 12
4x + 5y =-39
4x + 5y = -39
-4(-6y - 12) + 5y = -39
-4(-6y) + 4(12) + 5y = -39
24y + 48 + 5y = -39
29y + 48 = -39
29y = -87
y = -3
x = -6y - 12
x = -6(-3) - 12
x = 28 - 12
x = 6
(x, y) = (6, -3)
The equation is put in slope intercept form which is y=mx+b
The slope is m and in this case it is -1/2.
To find the y intercept substitute in 0
for x then solve.

Your answer would be C. 2