Dave wants to put a wooden frame around a mirror. The height of the mirror is 10 inches shorter than three times its width. Which equation represents the perimeter of the mirror, P, in terms of its width, w?
P=2(w + 3w - 10)
P=2(w - 3w – 10)
P=2(w + 3w + 10)
P=2(w – 3w + 10)