解方程 19-120%x=7 7/8x=21/40 x-28%x=3.6.

问题描述:

解方程
19-120%x=7                
7
8
x=
21
40
                 
x-28%x=3.6.

(1)19-120%x=7,
  19-120%x+120%x=7+120%x,
            19-7=7+120%x-7,
        12÷120%=120%x÷120%,
               x=10;
(2)

7
8
x=
21
40

 
7
8
x÷
7
8
=
21
40
÷
7
8

      x=
3
5

    
(3)x-28%x=3.6,
       72%x=3.6,
  72%x÷72%=3.6÷72%,
          x=5.