求未知数x (1)x+2/3x=15; (2)x-7/9x=4/3.

问题描述:

求未知数x 
(1)x+

2
3
x=15;                 (2)x-
7
9
x=
4
3

(1)x+

2
3
x=15
         
5
3
x=15
      
5
3
3
5
=15×
3
5

            x=9
(2)x-
7
9
x=
4
3

      
2
9
x=
4
3

   
2
9
9
2
=
4
3
×
9
2

        x=6