解方程和比例. ①4x+3×0.7=6.5 ②x:8=3/4:11/5 ③2x+2×0.7=4.5 ④x:8=1/4:1/5.

问题描述:

解方程和比例.

①4x+3×0.7=6.5 ②x:8=
3
4
:1
1
5
③2x+2×0.7=4.5 ④x:8=
1
4
1
5

①4x+3×0.7=6.5,
     4x+2.1-2.1=6.5-2.1,
             4x=4.4,
          4x÷4=4.4÷4,
              x=1.1;
②x:8=

3
4
:1
1
5

     1
1
5
x=8×
3
4

1
1
5
x÷1
1
5
=6÷1
1
5

       x=5;
③2x+2×0.7=4.5,
 2x+1.4-1.4=4.5-1.4,
         2x=3.1,
      2x÷2=3.1÷2,
          x=1.55;
④x:8=
1
4
1
5

   
1
5
x=8×
1
4

1
5
x÷
1
5
=2÷
1
5

     x=10.