Question 1170798
Original length = L
Original width = W
<pr>
2L + 2W = 200
<pr>
2(L - 20) + 2(0.75W) = 0.70(200)
<pr>
2L - 40 + 1.5W = 140
<pr>
2L + 1.5W = 180
<pr>
1.5W = 180 - 2L
<pr>
W = 180/1.5 - 2L/1.5
<pr>
W = 120 - 2L/1.5
<pr>
W = 120 - 4L/3
<pr>
Plug W = 120 - 4L/3 into the first equation:
<pr>
2L + 2W = 200
<pr>
2L + 2(120 - 4L/3) = 200
<pr>
2L + 240 - 8L/3 = 200
<pr>
2L - 8L/3 = -40
<pr>
6L/3 - 8L/3 = -40
<pr>
-2L/3 = -40
<pr>
-2L = -120
<pr>
L = 60
<pr>
Original length = L = <b>60m</b>