[tex]a)( \frac{2}{5} \div 2 \frac{1}{2} ) \times (4 \frac{1}{5} - 1 \frac{3}{40} ) + 1.35 \div 2.7 = ( \frac{2}{5} \div \frac{5}{2} ) \times ( \frac{21}{5} - \frac{43}{40} ) + \frac{135}{100} \div \frac{27}{10} = ( \frac{2}{5} \times \frac{2}{5} ) \times ( \frac{168}{40} - \frac{43}{40} ) + \frac{135}{100} \times \frac{10}{27} = \frac{4}{25} \times \frac{125}{40} + \frac{5}{10} = \frac{5}{10} + \frac{5}{10} = \frac{10}{10} = 1[/tex]
[tex]b) \frac{0.1}{(140 \frac{7}{30} - 138 \frac{5}{12}) \div18 \frac{1}{6} } = \frac{0.1}{( 140\frac{14}{60} - 138 \frac{25}{60}) \div 18 \frac{1}{6} } = \frac{0.1}{1 \frac{49}{60} \div 18 \frac{1}{6} } = \frac{0.1}{ \frac{109}{60} \times \frac{6}{109} } = \frac{0.1}{0.1} = 1[/tex]
[tex]c) \frac{1 \div 5}{(83 \frac{5}{18} - 85 \frac{7}{20} ) \div 2 \frac{2}{3} } = \frac{ \frac{1}{5} }{(83 \frac{50}{180} - 85 \frac{63}{180}) \div \frac{8}{3} } = \frac{ \frac{1}{5} }{ - 2 \frac{13}{180} \div \frac{8}{3} } = \frac{ \frac{1}{5} }{ - \frac{373}{180} \times \frac{3}{8} } = \frac{ \frac{1}{5} }{ - \frac{373}{480} } = - \frac{96}{373} [/tex]
