You would have to convert the 3 feet into inches. Since there are 12 inches in an foot you would do 3 times 12 and get 36. Then you would add the other 2 inches and get 38 inches. Next, you would do subtract 20 inches (that's how wide the chair is) from the 38 inches because you want to know how much wider the door is than the chair. Once you subtract 20 inches from 38 inches you get 18. The door is 18 inches wider than the chair.
18 inches or 1 foot and 6 inches multiply 3 feet by 12 and add two to get the width of the door in inches then subtract 20 inches from it to get the difference
