(1)3x+2.7=5.94,
3x+2.7-2.7=5.94-2.7,
3x=3.24,
3x÷3=3.24÷3,
x=1.08;
(2)x-0.1x=1.08,
(1-0.1)x=1.08,
0.9x÷0.9=1.08÷0.9,
x=1.2;
(3)1.3x-0.44=0.6,
1.3x-0.44+0.44=0.6+0.44,
1.3x=1.04,
1.3x÷1.3=1.04÷1.3,
x=0.8;
(4)4.5x÷3=0.9,
4.5x÷3×3=0.9×3,
4.5x=2.7,
4.5x÷4.5=2.7÷4.5,
x=0.6;
(5)6.7x+x=23.1,
( 6.7+1)x=23.1,
7.7x÷7.7=23.1÷7.7,
x=3;
(6)(7-1.4)x+5=7.8,
5.6x+5=7.8,
5.6x+5-5=7.8-5,
5.6x=2.8,
5.6x÷5.6=2.8÷5.6,
x=0.5.