4,2x+8.4=14.7

4,2х=14,7-8,4

4,2х=6,3

х=6,3/4,2

х=1,5

0.39*x-0.01=0.16

0.39*x=0.16+0.01

0.39*x=0.17

x=0.17/0.39

х=0,43589743589