7х+9=100 26х-0.8=7 1\2х-1\3=1\6 17.5х-0.5=34.5

1) 7x + 9 = 100
    7x = 100-9
    7х = 91
    х = 13
2) 26х-0.8=7
   26х = 7.8
   х = 0.3
3) 1/2x - 1/3=1/6
    1/2x=1/6+1/3
    1/2x=3/6
    1/2x=1/2
    x=1
4)17.5x-0.5=34.5
   17.5x=34.5+0.5
    17.5x=35
    x=2