Answer:
length = 24 meters
Step-by-step explanation:
1. l = 2w
2. P = 2l + 2w
P=72
3. 72 = 2l + 2w
4. Substitute w=l/2 to solve for l
72 = 2l + 2(l/2) ---> 72 = 3L - Divide by 3 on both sides
L= 24 meters
-3 X 7= -21