加减法的简便运算题 713-(387+313) =713-387-313 =713-313-387 =400-387 =13 866-370-130 =866-(370+130) =866-500 =366 400-199 =400-200+1 =200+1 =201 807-401 =800+7-400-1 =800+400+7-1 =1206 369-(246+69) =369-69-246 =300-246 =54