Original dimensions of the rectangular farm:
Width = 20 yards
Length = 40 yards.
If we were to enclose the original farm, we would need:
P = 2*20 + 2*40
P = 40 + 80 = 120 yards of fencing.
Note we have just calculated the perimeter of the rectangle, whose formula is:
P = 2W + 2L
We only have 88 yards of fencing available, so we need to reduce the length and the width by 2x yards, thus:
New Width = 20 - 2x
New Length = 40 - 2x
New perimeter:
P = 2(20 - 2x) + 2(40 - 2x)
Operating:
P = 40 - 4x + 80 - 4x
P = 120 - 8x
This is the length of the fencing, thus:
120 - 8x = 88
Subtracting 120:
-8x = 88 - 120
-8x = -32
Dividing by -8:
x = 4
The new dimensions of the farm are:
W = 20 - 2*4 = 12 yards
L = 40 - 2*4 = 32 yards
The dimensions of the farm are 12 x 32 yards