求未知数. 33/5:5.4=1.5:x 8.2x-60=4.2x+20 3x-10(10-x)=17.

问题描述:

求未知数.
3

3
5
:5.4=1.5:x      
8.2x-60=4.2x+20    
3x-10(10-x)=17.

(1)3

3
5
:5.4=1.5:x
            3
3
5
x=5.4×1.5
        3
3
5
x÷3
3
5
=8.1÷3
3
5

              x=2.25
(2)8.2x-60=4.2x+20
8.2x-60-4.2x=4.2x+20-4.2x
       4x-60=20
    4x-60+60=20+60
          4x=80
       4x÷4=80÷4
           x=20;
(3)3x-10(10-x)=17
          13x-100=17
      13x-100+100=17+100
              13x=117
          13x÷13=117÷13
                x=9.