解方程．910-x=25；5y-2y=0.12；27+x=12．

Question

解方程．
(9)/(10)-x=(2)/(5)；             5y-2y=0.12；             (2)/(7)+x=(1)/(2)．

Answer 1

①(9)/(10)-x=(2)/(5)
    (9)/(10)+x-x=(2)/(5)+x
       (2)/(5)+x=(9)/(10)
    (2)/(5)-(2)/(5)+x=(9)/(10)-(2)/(5)
         x=(1)/(2)


②5y-2y=0.12
     3y=0.12
  3y÷3=0.12÷3
      y=0.04


 ③(2)/(7)+x=(1)/(2)
(2)/(7)-(2)/(7)+x=(1)/(2)-(2)/(7)
     x=(3)/(14)