I have a word problem that i cant seem to figuered out. Can someone point me in the right direction.

A boat cruises 36mi against a 3mph current and 36 mi back in the direction of the same current. The round trip takes 5 hours what is the speed of the boat in still water?

I have drawns pictures look at other google examples and im afraid to say that im just stumped can someone help me figuered out this answer and explain how you got it?

Thanks