You must make the denominators equal to each other. (Remember anything you do to the top number you do to the bottom number!! (cross multiply))
- Multiply both 5 and 9 by 5 ( 5/9 turns into 25/45)
- Multiply both -4 and 5 by 9 ( -4/5 turns into -36/ 45)
- Solve as normal for your new problem 25/45 + (-36/45) = -11/45
