bai 1 :tong cua ba so tu nhien la 17 .biet rang so thu hai lon hon so thu nhat la 5 don vi va nho hon so thu ba 5 don vi .tim ba so do
bai 2 :khoi 5 dong dien the duc.neu cac em xep thanh 12 hang thi thua 5 hoc sinh.neu xep hang15 thi cung thua 5 ban nhung so hang it di 4 hang.hoi cobao nhieu hoc sinh dong dien ?