[tex]a) 2,1*\frac{2}{7} +\frac{4}{9} *1,8=\frac{21}{10} *\frac{2}{7} +\frac{4}{9} *\frac{18}{10} =\frac{3}{5} *\frac{1}{1} +\frac{2}{1} *\frac{2}{5} =\frac{3}{5} +\frac{4}{5} =\frac{7}{5} =1\frac{2}{5} \\\\b)0,54:\frac{3}{5} -\frac{1}{4} *0,1=\frac{54}{100} *\frac{5}{3} -\frac{1}{4} *\frac{1}{10} =\frac{18}{20} -\frac{1}{40} =\frac{36}{40} -\frac{1}{40} =\frac{35}{40} =\frac{7}{8}[/tex]
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