7х +5х+0.28=9,1
12x = 9,1-0,28
12x = 8,82
x = 8,82/12
x = 0.735
6х-14,7=22,05
6x = 22.05+14.7
6x = 36.75
x = 6.125
(5,8+х)•5,3=31,482
5.8+x = 31.482/5.3
5.8+x = 5.94
x = 5.94-5.8
x = 0.14
0,72:(0,8-х)=1,5
0.8-x = 0.72/1.5
0.8-x = 0.48
x = 0.8-0.48
x = 0.32
12-х:1,05=1,08
x/1.05 = 12-1.08
x/1.05 = 10.92
x = 10.92*1.05
x = 11.466