Answer:
10 families have cats
25 families have dogs
Step-by-step explanation:
The difference of ratio units is 5-2 = 3. The difference in pet counts is 15, so we can see that each ratio unit stands for 15/3 = 5 pets. Then ...
dogs : cats = 5 : 2 = (5·5) : (2·5) = 25 : 10
There are 10 families with cats and 25 families with dogs.