Adding and Subtracting Lengths

Jamilla, Andy, and Cassie are all classmates and are doing a group project. They chose to be in each other's group because they all live in the same neighborhood. Suppose Andy walked to Cassies's house and then he and Cassie both walked over to Jamilla's house.

Because they didn't finish the project until late, Andy walked Cassie home so she wasn't by herself. He then proceeded to walk back to his house.

How many blocks did Andy walk in all?