(1,65-0,3х):0,34=4,5
(1.65-0.3Х):0.34=4.5
1.65-0.3Х=4.5:0.34
1.65-0.3Х=1.53
0.3Х=1.65-1.53
0.3Х=0.12
Х=0.12:0.3
Х=0.4