The tripodasaurus has three legs. In a flock of tripodasauruses, there is a total of 20 heads and legs. How many tripodasauruses are in the flock? Think carefully first, then make a decision:
Each animal has 1 + 3 = 4 total heads and legs. Then there are 20 / 4 = 5 in the flock. So, the answer is 5.