Volume = length * width * height
441 = (x+7) * x * 12
All you have to do is just find x which is the width.
441 = (x+7) * 12x
441 = 12x2 + 84x
12x2 + 84x - 441 = 0
Thus you have a quadratic equation with two possible solution. Use the quadratic formula To calculate the x values. If you calculate it, you will find that x = 3.5 and x = -10.5. To prove which one is the width, substitute these values for x one at a time into the volume equation. Lets take x=3.5
441 = (x+7)+x+12
441 = (3.5+7) *3.5*12
441 = 10.5*3.5*12
441= 441
If we try -10.5;
441 = (x+7) *x*12
441=(-10.5+7)*10.5*12
441 = -3.5*10.5*12
441 = -441
Therefore clearly, our answer will be x = 3.5... We don't have to use the substitution to prove our answer is 3.5 because logically we can rule out -10.5 inches of width. Realistically, there can never be a negative width. Therefore your width is 3.5 inches. Hopefully this helps!
