How does 8 4/3 = 9 1/3?

You're question asks why the given mixed numbers are equal.

In fact, they're equal.

Lets make it easier for you to understand:

8 4/3 has a improper fraction "4/3", that fraction is over 1 whole.

You could look at 8 4/3 as:

8 + 3/3 + 1/3

The 3/3 turns into 1:

8 + 1 + 1/3

9 + 1/3

9 1/3

You would see that it turns into 9 1/3, therefore they are equal.