SOLUTION: Please...Please help i need to do this problem and i'm going to have a test tomorrow and i need to solve this but i don't know how to do it. The length of a rectangle is 20 yard

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Question 358218: Please...Please help i need to do this problem and i'm going to have a test tomorrow and i need to solve this but i don't know how to do it.
The length of a rectangle is 20 yards greater than the width. If the length was decreased by 5 yards, and the width increased by 4 yards, the area would remain unchanged. Find the original dimensions of the rectangle.
Answer by jsmallt9(3759) (Show Source):
You can put this solution on YOUR website!
Let x = original width
then
x + 20 = original width
This makes the original area, which is length * width: x*(x + 20) =

The new length (which is the original decreased by 5) = (x+20)-5 = x+15
The new width (which is the original width increased by 4): (x) + 4
This makes the new area: (x+15)(x+4) =

Since the area did not change, the new area equals the original area:

To solve this we will start by subtracting from each side:
19x + 60 = 20x
Subtracting 19x from each side:
60 = x

From the above we now know that the original width, x, was 60. The original length, x+20, would then be (60) + 20 = 80.