解方程 (1)2x-113/20+2.35=9 (2)x:7/10=0.3x+12.

问题描述:

解方程
(1)2x-1

13
20
+2.35=9           
(2)x:
7
10
=0.3x+12.

(1)2x-1

13
20
+2.35=9,
              2x+0.7=9,
          2x+0.7-0.7=9-0.7,
                  2x=8.3,
               2x÷2=8.3÷2,
                   x=4.15;     
      
(2)x:
7
10
=0.3x+12.
      x×
10
7
=0.3x+12,
       
10
7
x=
3
10
x+12,
 
100
70
x
21
70
x=
21
70
x-
21
70
x+12,
       
79
70
x=12,
  
79
70
70
79
=12×
70
79

           x=
840
79

           x=10
50
79