To change a fraction into a decimal, we divide the top number by the bottom number.
5/9 = 0.555…
Here is a simple diagram that shows only the long division part:

Detailed Explanation
Let’s divide 5 ÷ 9 step by step:
9 does not go into 5, so we start with 0.
Add a zero and look at 50.
9 goes into 50 five times (9 x 5 = 45).
Subtract: 50 – 45 = 5.
Bring down another zero – we get 50 again.
9 goes into 50 five times again… and the remainder is always 5.
Because the remainder keeps coming back as 5, the digit 5 keeps repeating forever. that’s why we write it as 0.5‾0.