0.3*7 4x=12.5 2.1 4x=12.5 4x=12.5-2.1 4x=10.4 x=10.4/4 x=2.6
0.3×7+4x=12.5
解: 2.1+4x=12.5
4x=12.5-2.1
4x=10.4
x=10.4÷4
x=2.6
2.1+4x=12.5
4x=12.5-2.1
4x=10.4
x=10.4/4
x=2.6
0.3x7+4x=12.5
2.1x+4x=12.5
6.1x=12.5
x=125/61
4x=12.5-2.1=10.4
解得:x=10.4/4=2.6