(1)3×7+4x=25
21+4x=25
21+4x-21=25-21
4x=4
4x÷4=4÷4
x=1;
(2)6x+18=48
6x+18-18=48-18
6x=30
6x÷6=30÷6
x=5;
(3)6x+x=42
7x=42
7x÷7=42÷7
x=6;
(4)1.2x-x=0.96
0.2x=0.96
0.2÷0.2x=0.96÷0.2
x=4.8.