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解方程. 6×4-0.5x=12.8 5x-2+1.8=3.6 7(x-1.2)=2.1.

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解方程.
6×4-0.5x=12.8 5x-2+1.8=3.6 7(x-1.2)=2.1.
(1)6×4-0.5x=12.8,
       24-0.5x=12.8,
  24-0.5x+0.5x=12.8+0.5x,
     0.5x+12.8=24,
0.5x+12.8-12.8=24-12.8,
          0.5x=11.2,
     0.5x÷0.5=11.2÷0.5,
             x=22.4;

(2)5x-2+1.8=3.6,
 5x-2+1.8-1.8=3.6-1.8,
         5x-2=1.8,
       5x-2+2=1.8+2,
           5x=3.8,
        5x÷5=3.8÷5,
            x=0.76;

(3)7(x-1.2)=2.1,
  7(x-1.2)÷7=2.1÷7,
          x-1.2=0.3,
      x-1.2+1.2=0.3+1.2,
              x=1.5.