解方程. 42x+25x=134 (x-3)÷2=7.5 13(x+5)=

解方程. 42x+25x=134 (x-3)÷2=7.5 13(x+5)=169.

(1)42x+25x=134,
             67x=134,
         67x÷67=134÷67,
               x=2;

(2)(x-3)÷2=7.5,
  (x-3)÷2×2=7.5×2,
            x-3=15,
          x-3+3=15+3,
              x=18;

(3)13(x+5)=169,
 13(x+5)÷13=169÷13,
           x+5=13,
        x+5-5=13-5,
            x=8.
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