Thực hiện phép tính (rút gọn kết quả nếu có thể) :
a) \({1 \over 8} + {{ - 5} \over 8}\) ; b) \({3 \over { - 20}} + {{ - 7} \over {20}}\);
c) \({{ - 5} \over 8} - {3 \over 4}\) ; d) \({5 \over {12}} - {{ - 7} \over {24}}\) ;
e) \({{ - 4} \over {15}} + {5 \over {12}}\) ; f) \({{ - 1} \over {16}} - {2 \over {15}}\) ;
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g) \( - 2 + {1 \over {14}}\) ; h) \({{ - 11} \over {12}} - \left( { - 1} \right)\).
\(\eqalign{ & a){1 \over 8} + {{ - 5} \over 8} = {{1 + ( - 5)} \over 8} = {{ - 4} \over 8} = {{ - 1} \over 2} \cr & b){3 \over { - 20}} + {{ - 7} \over {20}} = {{ - 3} \over {20}} + {{ - 7} \over {20}} = {{( - 3) + ( - 7)} \over {20}} = {{ - 10} \over {20}} = {{ - 1} \over 2} \cr & c){{ - 5} \over 8} - {3 \over 4} = {{ - 5} \over 8} - {6 \over 8} = {{ - 5} \over 8} + \left( { - {6 \over 8}} \right) = {{ - 5 + ( - 6)} \over 8} = {{ - 11} \over 8} \cr & d){5 \over {12}} - {{ - 7} \over {24}} = {{10} \over {24}} - {{ - 7} \over {24}} = {{10} \over {24}} + {7 \over {24}} = {{17} \over {24}} \cr & e){{ - 4} \over {15}} + {5 \over {12}} = {{ - 16} \over {60}} + {{25} \over {60}} = {{ - 16 + 25} \over {60}} = {9 \over {60}} = {3 \over {20}} \cr & f){{ - 1} \over {16}} - {2 \over {15}} = {{ - 15} \over {240}} - {{32} \over {140}} = {{ - 15} \over {240}} + {{ - 32} \over {240}} = {{ - 47} \over {240}} \cr & g) - 2 + {1 \over {14}} = {{ - 28} \over {14}} + {1 \over {14}} = {{ - 28 + 1} \over {14}} = {{ - 27} \over {14}} \cr & h){{ - 11} \over {12}} - ( - 1) = {{ - 11} \over {12}} + 1 = {{ - 11} \over {12}} + {{12} \over {12}} = {1 \over {12}} \cr} \)