a)Từ \( \displaystyle x.{3 \over 7} = {2 \over 3}\)
suy ra \( \displaystyle x = {2 \over 3}:{3 \over 7} \)
\( \displaystyle x= {2 \over 3}.{7 \over 3}\)
\( \displaystyle x= {{14} \over 9}\)
b)Từ \( \displaystyle x:{8 \over {11}} = {{11} \over 3}\)
suy ra \( \displaystyle x = {{11} \over 3}.{8 \over {11}} \)
\( \displaystyle x = {8 \over 3}\)
c)Từ \( \displaystyle {2 \over 5}:x = {{ - 1} \over 4}\)
suy ra \( \displaystyle x = {2 \over 5}:{{ - 1} \over 4} \)
\( \displaystyle x = {2 \over 5}.{4 \over { - 1}}\)
\( \displaystyle x = {8 \over { - 5}} \)
\( \displaystyle x= {{ - 8} \over 5}\)
d)Từ \( \displaystyle {4 \over 7}.x - {2 \over 3} = {1 \over 5}\)
suy ra \( \displaystyle {4 \over 7}.x = {1 \over 5} + {2 \over 3}\)
\( \displaystyle {4 \over 7}.x= {{3 + 10} \over {15}}\)
\( \displaystyle {4 \over 7} x = {{13} \over {15}}\)
\( \displaystyle x = {{13} \over {15}}:{4 \over 7} \)
\( \displaystyle x = {{13} \over {15}}.{7 \over 4} \)
\( \displaystyle x = {{91} \over {60}}\) .
e)Từ \( \displaystyle {2 \over 9} - {7 \over 8}.x = {1 \over 3}\)
suy ra \( \displaystyle {7 \over 8}.x = {2 \over 9} - {1 \over 3}\)
\( \displaystyle {7 \over 8}x = {{2 - 3} \over 9} = {{ - 1} \over 9}\)
\( \displaystyle x = {{ - 1} \over 9}:{7 \over 8} \)
\( \displaystyle x = {{ - 1} \over 9}.{8 \over 7}\)
\( \displaystyle x = {{ - 8} \over {63}}\)
g)Từ \( \displaystyle {4 \over 5} + {5 \over 7}:x = {1 \over 6}\)
Suy ra \( \displaystyle {5 \over 7}:x = {1 \over 6} - {4 \over 5}\)
\( \displaystyle {5 \over 7}:x = {{5 - 24} \over {30}}\)
\( \displaystyle {5 \over 7}:x ={{ - 19} \over {30}}\)
\( \displaystyle x = {5 \over 7}:{{ - 19} \over {30}}\)
\( \displaystyle x= {{5.30} \over {7.\left( { - 19} \right)}}\)
\( \displaystyle x= {{150} \over { - 133}} = {{ - 150} \over {133}}\)
