Answer:
C
Explanation:
Let the length be l and width be w.
The perimeter will be 2 lengths + 2 widths = 2l+2w
2l+2w cannot be more than 100ft
Also, the length has to be at least 10ft longer than the width.
If we substitute w=20, l=30. 2l+2w can be equal to 100 but not over it.
If w=20 and l=30, 2w+2l = 40+60 = 100.
Hence the maximum length of the width of the fence is 20 ft. C