Converting 0.66(repeating) to fractions is using the hack of if there is a single repeating digit, put that over 9. So, 0.6666(repeating) is 6/9 or 2/3. Now, 0.3 is 3/10.
Creating a qcd(quick common denominator) we have 20/30+9/30 = 29/30, which cannot be simplified further.
