Question 358218
Let x = original width
then
x + 20 = original width
This makes the original area, which is length * width: x*(x + 20) = {{{x^2 + 20x}}}<br>
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) = {{{x^2 + 19x + 60}}}<br>
Since the area did not change, the new area equals the original area:
{{{x^2 + 19x + 60 = x^2 + 20x}}}
To solve this we will start by subtracting {{{x^2}}} from each side:
19x + 60 = 20x
Subtracting 19x from each side:
60 = x<br>
From the above we now know that the original width, x, was 60. The original length, x+20, would then be (60) + 20 = 80.