Susanna and her sister had a bake sale, and earned 2/9 of the money. How much did they earn?

Two ninths. With ninths, it's an easy calculation. For instance:

1/9 = 0.1111111111111111111
2/9 = 0.22222222222222222
5/9 = 0.55555555555555555

You see the pattern!