$$\left. \begin{array} { l } { 12 \div ( 6 \times 2 ) = ( 172 \div 8 ) \times ( 12 \div 2 ) } \\ { ( a - b ) \div c = \frac { a b } { c } - \frac { ( b ) } { c } } \\ { 8 \div ( 15 - 13 ) = \frac { 8 } { 15 } - \frac { 8 } { 125 } } \end{array} \right.$$
