解方程. 3/4:5=3/5:x x-25%x=180 2/3x−1/5x=4.9.

问题描述:

解方程.

3
4
:5=
3
5
:x           
x-25%x=180
2
3
x
1
5
x=4.9.

(1)

3
4
:5=
3
5
:x 
          
3
4
x=5×
3
5

       
3
4
x÷
3
4
=3÷
3
4

            x=4
(2)x-25%x=180
       75%x=180
  75%x÷75%=180÷75%
          x=240
(3)
2
3
x
1
5
x=4.9
       
7
15
x=4.9
    
7
15
x÷
7
15
=4.9÷
7
15

           x=10.5.