6)    (4х+1)0.3=0.25*8.4
        1.2х+0.3=2.1
1.2х=2.1-0.3
1.2х=1.8
х=1.81.2
х=1.5

4)
(0.6х-2.5)*12.5=15*0.41
7.38х-30.75=6.15
7.38х=6.15+30.75
7.38х=36.9
х=36.97.38
х=5