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put this solution on YOUR website!Let x equal the width. (w)
Let 3x+12 equal the length. (l)
P = 2w + 2l
2(x) + 2(3x + 12) = 80
2x + 6x + 24 = 80
8x + 24 = 80
- 24 -24
8x = 56
/8 /8
x = 7
3x + 12 = 21 + 12 = 33
Check
2(7) + 2(33) = 80
14 + 66 = 80
80 = 80
The width is 7 feet and the length is 33 feet.