When you are dividing by a decimal, you have to move the decimal to the right however many places to make it a whole number. In this case if you move the decimal 1 place to the right (that means multiplying by 10) .8 becomes 8. However many places you move the decimal, you have to do the same for the other number. In this case 30.0 becomes 300. Now the problem becomes 300 ÷ 8.
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
