490-23-49-128
=498-(49+1+128+2+20)
490-(50+130+20)
=498-200
=298
245-125+355-175
=(245+355)-(125+175)
=600-300
=300267+186-267+186这题怎么进行简便计算呢 嘿嘿267+186-267+186=267-267+186*2=372