Can you explain how to solve this math problem: Barbie and Bruno have a pile of 144 coconuts that they need to move from one side of their yard to the other side.  Barbie can carry 4 coconuts at a time, while Bruno can carry 8 coconuts at a time.  If they make trips together carrying their maximum number of coconuts each time, how many trips together would they need to make to move all of the coconuts?