Question 1136533
 A rectangular athletic field has a length that is 20 yards longer than its width.
 Its original width will be increased by 4 yds and its length will be decreased by 5 yds.
 The new field will have an area that is the same as the original field.
 Find the dimensions of the original field. 
L = Length, W = width
:
L * W = (L-5)(W+4)
FOIL
LW = LW + 4L - 5w - 20
Subtract LW from both sides
0 = 4L - 5W - 20
"field has a length that is 20 yards longer than its width."
0 = 4(W+20) - 5W - 20
0 = 4W + 80 - 5W - 20
0 = -W + 60
W = 60 yds is the width of the original field
and
60 + 20 = 80 yds is the length
:
:
check
60 * 80 = 4800
64 * 75 = 4800