5. решить уравнения a) x-\frac{2}{5}x = 9 Б) х-\frac{1}{4}x = 7,5 B) x-\frac{7}{10}x = 1,8 Г) х-\frac{1}{3}x = 5

Решим уравнения:

1. a) $$x - \frac{2}{5}x = 9$$
2. $$1x - \frac{2}{5}x = 9$$
3. $$(\frac{5}{5} - \frac{2}{5})x = 9$$
4. $$\frac{3}{5}x = 9$$
5. $$x = 9 : \frac{3}{5}$$
6. $$x = 9 \cdot \frac{5}{3}$$
7. $$x = \frac{9 \cdot 5}{3}$$
8. $$x = \frac{45}{3}$$
9. $$x = 15$$

1. Б) $$x - \frac{1}{4}x = 7.5$$
2. $$1x - \frac{1}{4}x = 7.5$$
3. $$(\frac{4}{4} - \frac{1}{4})x = 7.5$$
4. $$\frac{3}{4}x = 7.5$$
5. $$x = 7.5 : \frac{3}{4}$$
6. $$x = 7.5 \cdot \frac{4}{3}$$
7. $$x = \frac{7.5 \cdot 4}{3}$$
8. $$x = \frac{30}{3}$$
9. $$x = 10$$

1. В) $$x - \frac{7}{10}x = 1.8$$
2. $$1x - \frac{7}{10}x = 1.8$$
3. $$(\frac{10}{10} - \frac{7}{10})x = 1.8$$
4. $$\frac{3}{10}x = 1.8$$
5. $$x = 1.8 : \frac{3}{10}$$
6. $$x = 1.8 \cdot \frac{10}{3}$$
7. $$x = \frac{1.8 \cdot 10}{3}$$
8. $$x = \frac{18}{3}$$
9. $$x = 6$$

1. Г) $$x - \frac{1}{3}x = 5$$
2. $$1x - \frac{1}{3}x = 5$$
3. $$(\frac{3}{3} - \frac{1}{3})x = 5$$
4. $$\frac{2}{3}x = 5$$
5. $$x = 5 : \frac{2}{3}$$
6. $$x = 5 \cdot \frac{3}{2}$$
7. $$x = \frac{5 \cdot 3}{2}$$
8. $$x = \frac{15}{2}$$
9. $$x = 7.5$$

Ответ: a) 15, Б) 10, В) 6, Г) 7.5