2 câu trả lời
XàPhòng
(278+352-10)-(278+352-20)
=(630-10)-(630-20)
=630-10-630+20
=(630-630)+(-10+20)
=0+10
=10
(278+352-10)-(278+352-20)
=278+352-10-278-352+20
=(278-278)+(352-352)+(-10+20)
=0+0+10
=10
XàPhòng
(278+352-10)-(278+352-20)
=(630-10)-(630-20)
=630-10-630+20
=(630-630)+(-10+20)
=0+10
=10
(278+352-10)-(278+352-20)
=278+352-10-278-352+20
=(278-278)+(352-352)+(-10+20)
=0+0+10
=10