To answer this question, you have to convert the given mixed number in a fractional number, then divide it by the weigh of each animal:

The answer is 6.
There is a certain number of animal on the scale, each one weighing 1/4, if the scale shows 1 1/2, to know how many animals are there on the scale we have to divide the weigh showed in the scale by the weigh of each animal. To do it the first step is to convert the mixed number to a fractional and then divide by 1/4 which is the weigh of the animals.