Tính :
\(\eqalign{ & a){2 \over 3} + {3 \over 8} – {5 \over {12}} \cr & b){{ – 3} \over {14}} + {3 \over 8} – {1 \over 4} \cr & c){5 \over 9}.\left( {{3 \over 5} + {3 \over {10}}} \right) \cr & d){1 \over 3} + {3 \over 4} – {7 \over {18}} \cr & e){1 \over 4} + {7 \over {12}} – {1 \over {11}} – {5 \over 8} \cr & f)\left( {{1 \over 5} + {3 \over {10}}} \right):\left( { – 2{1 \over 3}} \right). \cr} \)
\(\eqalign{ & a){2 \over 3} + {3 \over 8} – {5 \over {12}} = {{16} \over {24}} + {9 \over {24}} – {{10} \over {24}} = {{16 + 9 – 10} \over {24}} = {{15} \over {24}} = {5 \over 8} \cr & b){{ – 3} \over {14}} + {3 \over 8} – {1 \over 4} = {{ – 12} \over {56}} + {{21} \over {56}} – {{14} \over {56}} = {{ – 12 + 21 – 14} \over {56}} = {{ – 5} \over {56}} \cr & c){5 \over 9}.\left( {{3 \over 5} + {3 \over {10}}} \right) = {5 \over 9}.\left( {{6 \over {10}} + {3 \over {10}}} \right) = {5 \over 9}.{9 \over {10}} = {1 \over 2} \cr & d){1 \over 3} + {3 \over 4} – {7 \over {18}} = {{12} \over {36}} + {{27} \over {36}} – {{14} \over {36}} = {{12 + 27 – 14} \over {36}} = {{25} \over {36}} \cr & e){1 \over 4} + {7 \over {12}} – {1 \over {11}} – {5 \over 8} = {{66} \over {264}} + {{154} \over {264}} – {{24} \over {264}} – {{165} \over {264}} = {{66 + 154 – 24 – 165} \over {264}} = {{31} \over {264}} \cr & f)\left( {{1 \over 5} + {3 \over {10}}} \right):\left( { – 2{1 \over 3}} \right) = \left( {{2 \over {10}} + {3 \over {10}}} \right):\left( {{{ – 7} \over 3}} \right) = {5 \over {10}}.{{( – 3)} \over 7} = {{ – 3} \over {14}}. \cr} \)