Answer:
d. 40 feet
Step-by-step explanation:
Perimeter = 140 ft
Width = L + 10
P = 2w + 2L
140 = 2(L + 10) + 2L
140 = 2L + 20 + 2L
120 = 4L
L = 30
w = L + 10
w = 30 + 10
w = 40
