Let's simplify the equation step by step:

5.4x + (x + 0.2) 4.2 = 3.96
5.4x + 4.2 x + 0.2 * 4.2 = 3.96
5.4x + 4.2x + 0.84 = 3.96
(5.4 + 4.2)x + 0.84 = 3.96
9.6x + 0.84 = 3.96
9.6x = 3.12
x = 3.12 / 9.6
x = 0.325

Therefore, the solution to the equation is x = 0.325.