Question

[lehuyhoang]

khoi lop 3 cua truong doan ket gom 3 lop 3a,3b,3c.so hoc sinhcua ca khoi nhieu hon so hoc sinh cua lop 3c la 80 hs.lop 3b co it hon lop 3a la 2 hs.hoilop 3b co bao nhieu hs /?