Answer:
Length = 20 feet; x = 14
Step-by-step explanation:
Parameter = width + length + width + length
64 feet = 12 feet × 2 + (x + 6) feet × 2
64 = 24 + (x + 6) × 2
64 - 24 = (x + 6) × 2
40 = (x + 6) × 2
40 ÷ 2 = x + 6
20 = x + 6
20 = length
20 - 6 = x
14 = x
