(1)5x-0.4=2.4
5x-0.4+0.4=2.4+0.4
5x=2.8
5x÷5=2.8÷5
x=0.56;
(2)1-
x=2 27
1 9
1-
x+2 27
x=2 27
+1 9
x2 27
x=12 27
x+2 27
-1 9
=1-1 9
1 9
x=2 27
8 9
x÷2 27
=2 27
÷8 9
2 27
x=12;
(3)
x-3 4
x=2 5
7 10
x=7 20
7 10
x÷7 20
=7 20
÷7 10
7 20
x=2.