解方程. 1-25%x=0.75; 3/4x−25%x=10; 2x−1/8×4=2/3.

问题描述:

解方程.
1-25%x=0.75;

3
4
x−25%x=10;
2x−
1
8
×4=
2
3

(1)1-25%x=0.75
   1-25%x+25%x=0.75+25%x
             1=0.75+25%x
        1-0.75=0.75-25%x-0.75
          0.25=25%x
     0.25÷25%=25%x÷25%
             x=1;
(2)

3
4
x-25%x=10
         
1
2
x=10
      
1
2
1
2
=10÷
1
2

            x=20;
(3)2x−
1
8
×4=
2
3

          2x-
1
2
=
2
3

        2x-
1
2
+
1
2
=
2
3
+
1
2

             2x=
7
6

          2x÷2=
7
6
÷2

              x=
7
12