0,3 (0,4х-1,2)+0,36х=3,4

0.3 (0.4x-1.2)+0.36x=3.4 0.12x - 0.36 +0.36x =3.4 0.12x +0.36x - 0.36=3.4 0.48x -0.36=3.4 x= -0.36:0.48 x= -0.75