The unit rate for $240 per 4 days is $60 per 1 day.
To get a unit rate you must simplify the rate down to $X per 1 day.
To get 4 days down to 1 day you must divide 4 by 4.
Doing the same to the other side you divide 240 by 4.
So now you have $60 per 1 day.