0.54 repeating as a fraction is 54/99.
When a number that is not 0.99999...(etc) repeats, you need to add a digit 9 as to the denominator for every digit on top. For example, 0.2 repeating is 2/9, 0.21 repeating is 21/99, 213 repeating is 213/999, and so on.
You can always test this with a calculator to make sure.