For word problems, it is best to break them up. The problem states that there are 12 houses on a street. Each house has 4 pets. To find how many pets live on the street, you can do the following:
1/4 = 12/x
The equation below is a proportion. 1 house has 4 pets. We are trying to find the number of pets for 12 houses.
Knowing this you, can set a proportion as shown above, and cross multiply which would be 1 * x = 4 * 12
This reduces to x = 48 which will be your answer