Umk, OK bạn
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TL:
a) 3 x 5 + 2 x 3 + 3 x 3
= 3 x (5 + 2 + 3)
= 3 x 10
= 30
b) 2 x 9 + 5 x 9 + 27
= 2 x 9 + 5 x 9 + 3 x 9
= (2 + 5 + 3) x 9
= 10 x 9
= 90
HT