Kiểm tra :
\(\displaystyle {7 \over {12}} - \left( {{5 \over {12}} - {5 \over 6}} \right)\)\(\displaystyle ={7 \over {12}} - \left( {{5 \over {12}} - {10 \over 12}} \right) \)
\(\displaystyle = {7 \over 12} - \left( {-5 \over 12} \right) = {{12} \over {12}} = 1\)