设原来女生有x人则男生是(8/9)x现在女生x+1人男生是女生6/7所以(6/7)(x+1)=(8/9)x(6/7)x+6/7=(8/9)x(8/9)x-(6/7)x=6/7(8/9-6/7)x=6/7(2/63)x=6/7x=6/7÷(2/63)=27(8/9)x=24答：原来男生24人,女生27人...