X = -1.
Plug in the x-value.
![8(-1) - 2y = 10](https://tex.z-dn.net/?f=8%28-1%29%20-%202y%20%3D%2010)
![-8 - 2y = 10](https://tex.z-dn.net/?f=-8%20-%202y%20%3D%2010)
Add 8 to both sides.
![-2y = 18](https://tex.z-dn.net/?f=-2y%20%3D%2018)
Divide both sides by -2 to get y by itself.
![y = -9](https://tex.z-dn.net/?f=y%20%3D%20-9)
The value of y is
-9.
Let the volume of prism A be X. Then the volume of prism B is 2X. The combined volume could be described like this:
432 = X + 2X
Solving the equation,
432 = 3X
432/3=X
144=X
The volume of A is 144 cubic feet, while the volume of B is 288 cubic feet.
Lets call x how wide it is, and write the area equation:
area = width*length
a = (x)(x + 5) = 20000
expand it:
x^2 + 5x = 20000
make a quadratic trinomial:
x^2 + <span>5x - 20000 = 0
</span>lets apply the general quadratic formula to solve:
x = (-5 +- √(25 + 80000))/2
x = (-5 +- 282.89<span>)/2
we take the positive solution:
</span>x = (-5 + 282.89<span>)/2
</span>x = 138.94
therefore the rectangle width is 138.94 m and <span>143.94 m long</span>