You add the two numbers and divide by two to get their average, of the number that would be midway (also a midpoint for visualization) between them. Find the least common denominator, which should be 9. Thus, you will multiply both the numerator and denominator of 7/3 by 3 to retain the ratio. You should get 21/9. Now, add 21/9 and 5/9 to get 26/9. That should be your answer, but make it a mixed number so you don't have an improper fraction.
