求未知数x ①3x+1.25=5 ② 0.75- 1 4 x= 1 5 ③ 32:x= 4

求未知数x ①3x+1.25=5 ② 0.75- 1 4 x= 1 5 ③ 32:x= 4 9 : 5 8 ④0.8x+120%x=0.4.
2025-05-05 22:34:01
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回答1:

①3x+1.25=5,
 3x+1.25-1.25=5-1.25,
        3x÷3=3.75÷3,
            x=1.25;

②0.75-
1
4
x=
1
5

0.75-
1
4
x +
1
4
x=
1
5
+
1
4
x,
  
1
5
+
1
4
x-
1
5
=0.75-
1
5

      
1
4
x ÷
1
4
=0.55 ÷
1
4

           x=2.2;

③32:x=
4
9
5
8

  
4
9
x=32×
5
8

4
9
x ÷
4
9
=20 ÷
4
9

     x=45;

④0.8x+120%x=0.4,
         2x=0.4,
      2x÷2=0.4÷2,
          x=0.2.