William wants to hang a mirror in his room. The mirror and frame must have an area of 50 square feet. The mirror is 5 feet wide and 8 feet long. Which quadratic equation can be used to determine the thickness of the frame, x?
3x2 + 13x − 20 = 0
4x2 + 14x − 7 = 0
4x2 + 26x − 10 = 0
2x2 + 2x − 10 = 0