Each animal has two eyes. 50 eyes means there are 25 animals in all. 6 trunks tells you there are 6 elephants. Snakes have no legs, ostriches have two legs, and elephants have 4 legs. Since we already know there are 6 elephants we can see that 6 elephants x 4 legs/elephant = 24 elephant legs. That leaves 40 - 24 = 16 ostrich legs. At two legs per ostrich that gives us 8 ostriches. Finally we can see that 25 animals - 6 elephants - 8 ostriches = 11 snakes.