Answer:
Length = 42 feet
Width = 21 feet
Step-by-step explanation:
Let the length and width be represented by L and W
L = 2W
Perimeter (P) = 126 feet
2(L + W) = 126
L + W = 126/2 = 63
2W + W = 63
3W = 63
W = 63/3 = 21 feet
L = 2W = 2 × 21 feet = 42 feet