12 inches = 1foot 1yard = 3feet 6yards = 18feet Rerange the question: If edging cost $2.32 per 1foot stone, and you want a double layer of edging around your flower bed that is 18feet by 3feet. How much will edging you flower bed cost? Perimter: 2(18+3)=42 And since you want to double it; double the perimeter too. 42(2)=84