[tex]4) \\ \\ a) \frac{7}{8} \times \frac{2}{5} = \frac{7 \times 2}{8 \times 5} = \frac{14}{40} = \frac{7}{20} [/tex]
[tex]5) \\ \\ b) - \frac{11}{28} : \frac{33}{56} = - \frac{11}{28} \times \frac{56}{33} = - \frac{11 \times 56}{28 \times 33} = \frac{616}{924} = - \frac{2}{3} [/tex]
