30+70+10+90+20+80
=(30+70)+(10+90)+(20+80)
=100+100+100
=300
30 + 70 + 10 + 90 + 20 + 80
= ( 30 + 70 ) + ( 10 + 90 ) + ( 20 + 80 )
= 100 + 100 + 100
= 300
30 + 70 + 10 + 90 + 20 + 80
= ( 30 + 70 ) + ( 10 + 90 ) + ( 20 + 80 )
= 100 + 100 + 100
= 300
Chúc bạn học tốt!