Explain how you can find the amount of money Juan save if he earned $12 walking dogs

You can find how many he gets for each dog.

For example, let's pretend Juan gets $3 for each dog to walk, then he would've walked 4 dogs. But in this real problem we don't know how much he gets for each dog.

So, you can find the amount of money Juan saved by knowing how much is for each dog walked.