<span>3^(x+2) - 2*3^(x+1) + 3^x < 12</span>
3^x * 9 - 2*3^x * 3 + 3^x < 12
3^x ( 9 - 6 + 1) < 12
3^x *4 < 12
3^x < 3^1
x < 1
21-3x<2x+5
-3x-2x<5-21
-5x<-16
x<3,2
( ( 5X - 3) / 3 ) - 1 = ( 5X - 3 - 3) / 3 = ( 5X - 6) / 3
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(5X - 6)*12 = ( 5X - 3)*3
60X - 72 = 15X - 9
60X - 15X = - 9 + 72
45X = 63
X = 1.4