№5 Выполни действия a) 10 7 10 x 7 70 X = = 11 9 □×□ □ б) 4 33 □×33 3 X = = × 3 = 11 37. 1× □ в) 3 8 □× □× □ x-=-= = 4 9 □× □× □ г) 16 9 4 X = = 27 20 15

a) $$\frac{10}{11} \times \frac{7}{9} = \frac{10 \times 7}{11 \times 9} = \frac{70}{99}$$

б) $$\frac{4}{11} \times \frac{33}{37} = \frac{4 \times 33}{11 \times 37} = \frac{4 \times 3}{1 \times 37} = \frac{12}{37}$$

в) $$\frac{3}{4} - \frac{8}{9} = \frac{3 \times 9}{4 \times 9} - \frac{8 \times 4}{9 \times 4} = \frac{27}{36} - \frac{32}{36} = -\frac{5}{36}$$

г) $$\frac{16}{27} \times \frac{9}{20} = \frac{4}{15}$$

Ответ: a) $$\frac{70}{99}$$, б) $$\frac{12}{37}$$, в) $$\frac{-5}{36}$$, г) $$\frac{4}{15}$$