John currently has a square garden. He wants to redesign his garden and make it into a rectangle with a length that is 3 feet shorter than twice its width. He decides that the perimeter should be 60 feet. Determine the dimensions, in feet, of his new garden. Please show work.
P = 2L + 2W
60 = 2(2W - 3) + 2W
60 = 6W - 6
66 = 6W
11 = W