The answer is 3_4/11. The "_" indicates it's not the same number. So you don't get confused.
When repeating, you put a 99. Not 100. So, this will be 36/99. Now, you simplify. Also add the 3. You then get 3_4/11.
Proof:
x=0.6...
10x=6.6...
-x=0.6...
9x=6
x=2/3
2/3=0.6...
