coi so hoc sinh nu la 5 phan bang nhau thi coi so hoc sinh nam la 7 phan nhu the
hieu so phan bang nhau la:
7-5=2(phan)
so hoc sinh nam cua lop 4a la:
6:2*7=21(hs)
so hoc sinh nu cua lop 4a la:
21-6=15((hs)
Tong so hoc sinh ca lop la:
21+15=36(hs)
D/s:36hs