5кл помогите пожалуйста дроби

Решите задачу:

$1) \frac{5}{9} *4 = \frac{5*4}{9} = \frac{20}{9} = 2 \frac{2}{9} \\ \\ 2) \frac{a}{b} *c = \frac{a*c}{b} \\ \\ 3) \\ \\ \frac{7}{10} *30 = \frac{7*30}{10} = \frac{210}{10} = \frac{21}{1} =21 \\ \\ \frac{4}{15} *50 = \frac{4*50}{15} = \frac{200}{15} = \frac{40}{3} = 13 \frac{1}{3} \\ \\ 3* \frac{5}{12} = \frac{3*5}{12} = \frac{5}{4} = 1 \frac{1}{4} \\ \\ c* \frac{a}{b} = \frac{c*a}{b}$