1) 10x-11 = 4x - 7 2) 14x-25 = 20x + 9 3) -3(5-x) = 35-5x 4) 14x + 3 = 8x - 43 5) 18x + 9=32x + 14 6) 0,8(x - 2) + 2,6 = 0,5(7 + x) 7) -0,5(x - 4) - 7,3 = 0,8(2 – x) 8) (x+7)/(x+9) = 3/4 9) (x-7)/9 = (4-x)/7 11) 3/x-7 = 2/(4-x) 11) (1,2x-2)(8x + 5,6) = 0 12) (8y + 6)(1,8 – 0,4y) = 0

Решение уравнений:

1. 10x - 11 = 4x - 7

   10x - 4x = 11 - 7

   6x = 4

   x = 4/6 = 2/3

   Ответ: x = 2/3

2. 14x - 25 = 20x + 9

   14x - 20x = 25 + 9

   -6x = 34

   x = -34/6 = -17/3

   Ответ: x = -17/3

3. -3(5 - x) = 35 - 5x

   -15 + 3x = 35 - 5x

   3x + 5x = 15 + 35

   8x = 50

   x = 50/8 = 25/4

   Ответ: x = 25/4

4. 14x + 3 = 8x - 43

   14x - 8x = -3 - 43

   6x = -46

   x = -46/6 = -23/3

   Ответ: x = -23/3

5. 18x + 9 = 32x + 14

   18x - 32x = 9 + 14

   -14x = 23

   x = -23/14

   Ответ: x = -23/14

6. 0,8(x - 2) + 2,6 = 0,5(7 + x)

   0,8x - 1,6 + 2,6 = 3,5 + 0,5x

   0,8x + 1 = 3,5 + 0,5x

   0,8x - 0,5x = 3,5 - 1

   0,3x = 2,5

   x = 2,5 / 0,3 = 25/3

   Ответ: x = 25/3

7. -0,5(x - 4) - 7,3 = 0,8(2 – x)

   -0,5x + 2 - 7,3 = 1,6 - 0,8x

   -0,5x - 5,3 = 1,6 - 0,8x

   -0,5x + 0,8x = 1,6 + 5,3

   0,3x = 6,9

   x = 6,9 / 0,3 = 69/3 = 23

   Ответ: x = 23

8. \[ \frac{x+7}{x+9} = \frac{3}{4} \]

   4(x+7) = 3(x+9)

   4x + 28 = 3x + 27

   4x - 3x = 27 - 28

   x = -1

   Ответ: x = -1

9. \[ \frac{x-7}{9} = \frac{4-x}{7} \]

   7(x-7) = 9(4-x)

   7x - 49 = 36 - 9x

   7x + 9x = 36 + 49

   16x = 85

   x = 85/16

   Ответ: x = 85/16

10. \[ \frac{3}{x-7} = \frac{2}{4-x} \]

    3(4-x) = 2(x-7)

    12 - 3x = 2x - 14

    12 + 14 = 2x + 3x

    26 = 5x

    x = 26/5

    Ответ: x = 26/5

11. (1,2x - 2)(8x + 5,6) = 0

    1,2x - 2 = 0 или 8x + 5,6 = 0

    1,2x = 2 или 8x = -5,6

    x = 2 / 1,2 = 20/12 = 5/3 или x = -5,6 / 8 = -56/80 = -7/10

    Ответ: x = 5/3; x = -7/10

12. (8y + 6)(1,8 – 0,4y) = 0

    8y + 6 = 0 или 1,8 - 0,4y = 0

    8y = -6 или 1,8 = 0,4y

    y = -6/8 = -3/4 или y = 1,8 / 0,4 = 18/4 = 9/2

    Ответ: y = -3/4; y = 9/2