The LCD of the denominator is 12. For this one it is possible to just 'see' that 6 is a divisor of 12. When in doubt, you can always get an answer by just multiplying the denominators. (ie., you can turn 11/12 into 66/72 and 1/6 into 12/72).
In this case, the easiest is to convert 1/6 into 2/12. (multiply both numbers by 2).
Then it becomes:
[tex]9\frac{11}{12} - 9 \frac 2{12} = 9 \frac{11-2}{12} - 9 = \frac9{12} = \frac34[/tex]
