0,5(x - 9) = 0,3(2 + x) + 0,8;

0.5x - 4.5 = 0.6 + 0.3x + 0.8;

0.5x - 0.3x = 0.6 + 0.8 + 4.5;

0.2x = 5,9;

x = 5.9 : 0.2;

x = 29.5.