Answer:
10 feet
Step-by-step explanation:
18 × 2 = 36
56 - 36 = 20
20 ÷ 2 = 10
To check work, add all lengths together. 4 sides. 18 + 18 + 10 + 10 = 56
10
(length + width) * 2 = 56 -->
length + width = 28
length = 18 -->
18 + width = 28 -->
width = 10
