问题 解答题
计算:
3:8=X:2.4
X:5=
2
5
:0.5
7
8
:X=6:8
12X=300-4X7X+5.3=7.4(200-X)÷5=30.
答案

(1)3:8=x:2.4,

          8x=3×2.4,

       8x÷8=7.2÷8,

           x=0.9,

(2)x:5=

2
5
:0.5,

    0.5x=5×

2
5

0.5x÷0.5=2÷0.5,

        x=4,

(3)

7
8
:x=6:8,

       6x=

7
8
×8,

    6x÷6=7÷6,

        x=

7
6

(4)12x=300-4x,

  12x+4x=300-4x+4x,

     16x=300,

 16x÷16=300÷16,

       x=18.75,

(5)7x+5.3=7.4,

7x+5.3-5.3=7.4-5.3,

        7x=2.1,

     7x÷7=2.1÷7,

         x=0.3,

(6)(200-x)÷5=30,

  (200-x)÷5×5=30×5,

           200-x=150,

     200-x+x-150=150+x-150,

              50=x,

               x=50.

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