81. Решите уравнение: 1) \frac{8}{9}x = \frac{2}{9}; 3) \frac{4}{7}x = 16; 5) x:\frac{9}{16} = \frac{32}{45}; 2) \frac{5}{9}x = 1; 4) 5x = \frac{4}{5}; 6) 7\frac{1}{5}:x = \frac{9}{10}.

Решим уравнения:

1)

$$\frac{8}{9}x = \frac{2}{9}$$

$$x = \frac{2}{9}:\frac{8}{9}$$

$$x = \frac{2}{9} \cdot \frac{9}{8}$$

$$x = \frac{1}{4}$$

Ответ: $$\frac{1}{4}$$

2)

$$\frac{5}{9}x = 1$$

$$x = 1:\frac{5}{9}$$

$$x = \frac{9}{5}$$

$$x = 1\frac{4}{5}$$

Ответ: $$1\frac{4}{5}$$

3)

$$\frac{4}{7}x = 16$$

$$x = 16:\frac{4}{7}$$

$$x = 16 \cdot \frac{7}{4}$$

$$x = 4 \cdot 7$$

$$x = 28$$

Ответ: 28

4)

$$5x = \frac{4}{5}$$

$$x = \frac{4}{5}:5$$

$$x = \frac{4}{5} \cdot \frac{1}{5}$$

$$x = \frac{4}{25}$$

Ответ: $$\frac{4}{25}$$

5)

$$x:\frac{9}{16} = \frac{32}{45}$$

$$x = \frac{32}{45} \cdot \frac{9}{16}$$

$$x = \frac{2}{5} \cdot \frac{1}{1}$$

$$x = \frac{2}{5}$$

Ответ: $$\frac{2}{5}$$

6)

$$7\frac{1}{5}:x = \frac{9}{10}$$

$$\frac{36}{5}:x = \frac{9}{10}$$

$$x = \frac{36}{5}:\frac{9}{10}$$

$$x = \frac{36}{5} \cdot \frac{10}{9}$$

$$x = \frac{4}{1} \cdot \frac{2}{1}$$

$$x = 8$$

Ответ: 8