2. Решите уравнения a) ((15-2(18:x+2))-18+9): 11 = 9 б)$$\frac{2}{5}$$·x+x+4·x = $$\frac{9}{25}$$

2. Решите уравнения

a) ((15-2(18:x+2))-18+9): 11 = 9

1. ((15-2(18:x+2))-18+9) = 9 × 11
2. ((15-2(18:x+2))-18+9) = 99
3. 15-2(18:x+2)-18+9 = 99
4. 15-2(18:x+2)-9 = 99
5. 15-2(18:x+2) = 99+9
6. 15-2(18:x+2) = 108
7. -2(18:x+2) = 108 - 15
8. -2(18:x+2) = 93
9. 18:x+2 = 93 : (-2)
10. 18:x+2 = -46.5
11. 18:x = -46.5 - 2
12. 18:x = -48.5
13. x = 18 : (-48.5)
14. x = -0.3711

Ответ: x = -0.3711

б)$$\frac{2}{5}$$·x+x+4·x = $$\frac{9}{25}$$

1. $$\frac{2}{5}x + x + 4x = \frac{9}{25}$$
2. $$\frac{2}{5}x + 5x = \frac{9}{25}$$
3. $$\frac{2x + 25x}{5} = \frac{9}{25}$$
4. $$\frac{27x}{5} = \frac{9}{25}$$
5. $$27x = \frac{9 \cdot 5}{25}$$
6. $$27x = \frac{9}{5}$$
7. x = $$\frac{9}{5}$$ : 27
8. x = $$\frac{9}{5 \cdot 27}$$
9. x = $$\frac{1}{5 \cdot 3}$$
10. x = $$\frac{1}{15}$$

Ответ: x = 1/15