草地上有白兔、灰兔和黑兔一共20只，白兔的只数比灰兔只数的7倍多，8倍少。草地上灰兔(k*g0J8[6t7U/E9G;}4['j5Y;Q7E*E3?)t只，白兔3X9~:C-b只，黑兔9Q'H2g*p/?5t只。:q-S9]6X0X3}.n2r0|1Q-Y5I