Открываем скобки:

5.6 - 3 * (2 - 0.4x) = 0.4 * (4x + 1);

5.6 - 3 * 2 + 3 * 0.4x = 0.4 * 4x + 0.4 * 1;

5.6 - 6 + 1.2x = 1.6x + 0.4;

1.2x - 1.6x = 0.4 + 6 - 5.6;

x(1.2 - 1.6) = 6.4 - 5.6;

-0.4x = -0.8;

x = 2.