50,000 years = 1 hour.
So if you multiply or divide one side of the equation by something you need to do the same to the other side.
Now you want 50,000 to become 80. So what do you multiply 50,000 by to get 80.
Well if you divide 50,000 by 50,000 you get 1. Now if you multiply 1 by 80, you'll get 80. Putting this together we have that 50,000*(80/50,000) = 80.
Now the other side is 1hr*(80/50,0000) or 60 min(80/50,000) or 3600sec(80/50,000)=....