\(\frac{\left(\frac{1}{2}-0,75\right).\left(0,2-\frac{2}{5}\right)}{\frac{5}{9}-1\frac{1}{12}}=\frac{\left[0,25.\left(2-3\right)\right].\left[0,2.\left(1-2\right)\right]}{\frac{5}{9}-\frac{13}{12}}\)

\(=\frac{0,25.1-0,2.1}{\frac{20}{36}-\frac{39}{36}}=\frac{\frac{1}{20}}{-\frac{19}{36}}=\frac{-9}{95}\)

Xin lỗi nhé , phần này chỉ tính nhanh được ở tử chứ mẫu số không được đâu 

\(\frac{\left(\frac{1}{2}-0,75\right).\left(0,2-\frac{2}{5}\right)}{\frac{5}{9}-1\frac{1}{2}}\)

\(=\frac{\left(0,5-0,75\right).\left(\frac{1}{5}-\frac{2}{5}\right)}{\frac{5}{9}-\frac{3}{2}}\)

\(=\frac{\left(-0,25\right).\frac{-1}{5}}{\frac{10}{18}-\frac{27}{18}}\)

\(=\frac{\frac{-1}{4}.\frac{-1}{5}}{-\frac{17}{18}}\)

\(=\frac{\frac{1}{20}}{-\frac{17}{18}}\)

\(=\frac{1}{20}.\frac{-18}{17}\)

\(=\frac{-18}{340}\)

\(=\frac{-9}{170}\)

a,\(\frac{-9}{95}\)

b,\(\frac{-2}{3}\)

k nha

\(a,=\frac{24}{60}+\left(-\frac{10}{60}\right)-\frac{45}{60}+\frac{40}{60}\)

         \(=\frac{24+\left(-60\right)-45+40}{60}\)

      \(=-\frac{41}{60}\)

Kiral Kiral kết bạn nhé. Mình cũng ở tỉnh Hà Tĩnh

a)\(\frac{3}{20}\)

b)\(\frac{-1}{4}\)

c)\(\frac{-9}{95}\)

đúng thì k cho mk nha

b)=(2/3 +2/7 - 2/28)/(-3/3 -3/7 + 3/28)

=[2(1/3+1/7-1/28)]/[(-3)(1/3+1/7-1/28)]

=2/-3 

=-2/3

\(=\frac{-\frac{1}{4}.-\frac{1}{5}}{\frac{5}{9}-\frac{13}{12}}\)

\(=\frac{\frac{1}{20}}{\frac{1}{4}}\)

\(=\frac{1}{20}:\frac{1}{4}\)

\(=\frac{1}{5}\)

\(a)\frac{2}{{15}} + \left( {\frac{{ - 5}}{{24}}} \right) = \frac{{16}}{{120}} + \left( {\frac{{ - 25}}{{120}}} \right) = \frac{{ - 9}}{{120}} = \frac{{ - 3}}{{40}}\)          

 b) \(\left( {\frac{{ - 5}}{9}} \right) - \left( { - \frac{7}{{27}}} \right) = \left( {\frac{{ - 15}}{{27}}} \right) + \frac{7}{{27}} = \frac{{ - 8}}{{27}}\)          

 c)\(\left( { - \frac{7}{{12}}} \right) + 0,75 = \left( { - \frac{7}{{12}}} \right) + \frac{75}{100} \\= \left( { - \frac{7}{{12}}} \right) + \frac{3}{4} \\= \left( { - \frac{7}{{12}}} \right) + \frac{9}{{12}} = \frac{2}{{12}} = \frac{1}{6}\)

d)\(\left( {\frac{{ - 5}}{9}} \right) - 1,25 =\left( {\frac{{ - 5}}{9}} \right) - \frac{125}{100} = \left( {\frac{{ - 5}}{9}} \right) - \frac{5}{4}\\ = \left( {\frac{{ - 20}}{{36}}} \right) - \frac{{45}}{{36}} = \frac{{ - 65}}{{36}}\)       

 e)\(0,34.\frac{{ - 5}}{{17}} =\frac{{34}}{{100}}.\frac{{ - 5}}{{17}} = \frac{{17}}{{50}}.\frac{{ - 5}}{{17}} = \frac{{ - 1}}{{10}}\)                       

g) \(\frac{4}{9}:\left( { - \frac{8}{{15}}} \right) = \frac{4}{9}.\left( { - \frac{{15}}{8}} \right) = \frac{{ - 5}}{6}\)

h)\(\left( {1\frac{2}{3}} \right):\left( {2\frac{1}{2}} \right) = \frac{5}{3}:\frac{5}{2} = \frac{5}{3}.\frac{2}{5} = \frac{2}{3}\)       

i) \(\frac{2}{5}.\left( { - 1,25} \right) = \frac{2}{5}.\frac{{ - 125}}{100} = \frac{2}{5}.\frac{{ - 5}}{4} = \frac{{ - 1}}{2}\)                     

k) \(\left( {\frac{{ - 3}}{5}} \right).\left( {\frac{{15}}{{ - 7}}} \right).3\frac{1}{9} = \left( {\frac{{ - 3}}{5}} \right).\left( {\frac{{15}}{{ - 7}}} \right).\frac{{28}}{9}\\ = \frac{{ - 3.3.5.7.4}}{{5.\left( { - 7} \right).3.3}} = 4\)