Приведем уравнение к более простому виду:
3(2.5x - 0.2) - 15.2 = 6 - (2/3 x - 0.5x)
7.5x - 0.6 - 15.2 = 6 - (2/3 - 1/2)x
7.5x - 15.8 = 6 - (4/6 - 3/6)x
7.5x - 15.8 = 6 - 1/6 x
7.5x + 1/6 x = 6 + 15.8
(45/6 + 1/6)x = 21.8
46/6 x = 21.8
23/3 x = 21.8
x = 21.8 * 3 / 23 ≈ 2.83