[tex](1 \frac{2}{5} + 0.5) \div 2 = ( \frac{7 \times 2}{5 \times 2} + \frac{1 \times 5}{2 \times 5} ) \div 2 = ( \frac{14}{10} + \frac{5}{10} ) \div 2 = \frac{19}{10} \times \frac{1}{2} = \frac{19}{20} [/tex]
[tex] \frac{5}{8} \times 4.2 - \frac{1}{4} = \frac{ \not5 {}^{1} }{8} \times \frac{21}{ \not5 {}^{1} } - \frac{1}{4} = \: \frac{21}{8} - \frac{1 \times 2}{4 \times 2} = \frac{21}{8} - \frac{2}{8} = \frac{19}{8} = 2 \frac{3}{8} [/tex]
[tex] \frac{4}{7} \times (0.2 + \frac{1}{4} ) = \frac{4}{7} \times ( \frac{1 \times 4}{5 \times 4} + \frac{1 \times 5}{4 \times 5} ) = \frac{4}{7} \times ( \frac{4}{20} + \frac{5}{20} ) = \frac{ \not4 {}^{1} }{7} \times \frac{9}{\not20 {}^{5} } = \frac{9}{35} [/tex]
