解方程: x-4/9x=10/21 x:4/7=5/8:11/12 6.4Χ=0.12:1.5.

问题描述:

解方程:
x-

4
9
x=
10
21

x:
4
7
=
5
8
11
12

6.4
Χ
=0.12:1.5.

(1)x-

4
9
x=
10
21

    (1-
4
9
)x=
10
21

      
5
9
5
9
=
10
21
÷
5
9

           x=
6
7

(2)x:
4
7
=
5
8
11
12

      
11
12
x=
4
7
×
5
8

 
11
12
11
12
=
5
14
÷
11
12

        x=
30
77

(3)
6.4
Χ
=0.12:1.5,
      0.12x=6.4×1.5,
      0.12x=9.6,
0.12x÷0.12=9.6÷0.12,
          x=80.