Question 179540
Let x = width
and y = length
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From:"A concrete driveway has a perimeter of 280 feet" we get:
2(x+y) = 280
2x+2y = 280 
x + y = 140 (equation 1)
.
From:"The length of the driveway is 20 feet more than 4 times its width."
y = 4x+20  (equation 2)
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Using the definition of y from equation 2 substitute it into equation 1 and solve for x:
x + y = 140 
x + 4x+20 = 140 
5x+20 = 140
5x = 120
x = 24 feet (width)
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Substitute the above into equation 2 and solve for y:
y = 4x+20
y = 4(24)+20
y = 96+20
y = 116 feet (length)