. Goi so hoc sinh lop 8a la x (dk athuoc N*)
ta co so hsg lop 8a o hoc ki 1 la x/6
so hsg lop 8a o hoc ki 2 la 2x/9
Vi sang hoc ki 2 co them 2 ban tro thanh hoc sinh gioi nen ta co phuong trinh
2x/9 −a/6 =2⇒a=36(tmdkdb)
Vay lop 8a co 36 hoc sinh