Answers ( 4 )
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20 + 30 + 40 + 50 + 60 + 70
= ( 70 + 30 ) + ( 40 + 60 ) + (20 + 50 )
= 100 + 100 + 70
= 200 + 70
= 270
Tk mk nha m.n !! ^^
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