Sabrina has a rug with a perimeter of 18 feet. She decides to place a border around the rug so that the new length of the rug is 8 feet and the width is 4 feet. The border is the same width all the way around. A rectangle has a length of 8 feet and width of 4 feet. The equation which represents x, the width of the border is 2 (8 minus 2 x) + 2 (4 minus 2 x) = 18. What is the width of the border?