5,4*(х+0,2)+4,2х=3,96

5,4*(х+0,2)+4,2х=3,96
5,4х+1,08+4,2х=3,96
5,4х+4,2х=3,96-1,08
9,6х=2,88/:9,6
х=0,3

5.4*( x+0.2 ) + 4.2 = 3.96
5.4x + 1.08 + 4.2x = 3.96
5.4x + 4.2x = 3.96 - 1.08
9.6x = 2.88
x = 2.88 : 9.6
x = 0.3