A) 5,5(x + 1) = 1/2(2 - x) b)3,5(3x - 1)

а) 5,5 * (x + 1) = 1/2 * (2 - x);

5,5х + 5,5 = 1 - 0,5х;

5,5х + 0,5х = 1 - 5,5;

6х = -4,5;

х = -4,5 : 6;

х = -0,75;

5,5 * (-0,75 + 1) = 1/2 * (2 - (-0,75));

5,5 * 0,25 = 0,5 * 2,75;

1,375 = 1,375;

b) 3,5 * (3x - 1) - 2 1/2 * (x - 3) = 0;

2 1/2 = 5/2 = 2,5; 

10,5х - 3,5  - 2,5х + 7,5 = 0;

8х = -4;

х = -0,5;

3,5 * (3 * (-0,5) - 1) - 2 1/2 * (-0,5 - 3) = 0;

3,5 * (-2,5) - 2,5 * (-3,5) = 0;

-8,75 + 8,75 = 0;

0 = 0.

c) Раскроем скобки и упростим выражение:

3/4 * (x + 2) + 2/5 * (x - 1) - 21/40 = 3/4х + 6/4 + 2/5х - 2/5 - 21/40 = 3/4х + 2/5х + 6/4 -

- 2/5 - 21/40 = 15/20х + 8/20х + 60/40 - 16/40 - 21/40 = 23/20х + 23/40.