Bài 99 trang 49 SGK Toán 7 tập 1

\(\eqalign{
& P = \left( { - 0,5 - {3 \over 5}} \right):\left( { - 3} \right) + {1 \over 3} - \left( { - {1 \over 6}} \right):\left( { - 2} \right) \cr
& = \left( { - {1 \over 2} - {3 \over 5}} \right):\left( { - 3} \right) + {1 \over 3} - \left( { - {1 \over 6}} \right).\left( { - {1 \over 2}} \right) \cr
& = {{ - 5 - 6} \over {10}}:\left( { - 3} \right) + {1 \over 3} - {1 \over {12}} \cr
& = {{ - 11} \over {10}}:\left( { - 3} \right) + \left( {{4 \over {12}} - {1 \over {12}}} \right) \cr
& = {{ - 11} \over {10}}.\left( { - {1 \over 3}} \right) + {3 \over {12}} \cr
& = {{11} \over {30}} + {1 \over 4} = {{22} \over {60}} + {{15} \over {60}} = {{37} \over {60}} \cr
& Q = \left( {{2 \over {25}} - 1,008} \right):{4 \over 7}:\left[ {\left( {3{1 \over 4} - 6{5 \over 9}} \right).2{2 \over {17}}} \right] \cr
& = \left( {{2 \over {25}} - {{1008} \over {1000}}} \right):{4 \over 7}:\left[ {\left( {{{13} \over 4} - {{59} \over 9}} \right).{{36} \over {17}}} \right] \cr
& = \left( {{{10} \over {125}} - {{126} \over {125}}} \right):{4 \over 7}:\left[ {\left( {{{117} \over {36}} - {{236} \over {36}}} \right).{{36} \over {17}}} \right] \cr
& = \left( {{{ - 116} \over {125}}} \right).{7 \over 4}:\left( {{{ - 119} \over {36}}.{{36} \over {17}}} \right) \cr
& = {{ - 29.7} \over {125.1}}:\left( { - 7} \right) = {{ - 29.7} \over {125}}.{{ - 1} \over 7} = {{29} \over {125}} \cr} \)