3/8 of this room is rust and 5/2 of this room is dust and dirt!!
First I need to change the second number to a negative and get common denominators. That would turn it to this: 3/8+20/8.
Then you subtract 20/8 from 3/8 and get 17/8. Since that is an improper fraction you turn 17/8 into 2 1/8. So, 2 1/8 of this room was rust and dirt before I cleaned it and remodeled it. Now it looks brand new!!!