Let x = the speed of the boat in still water, in miles per hour.


Then in the fall, the time upstream is   hours.


     in the spring, the time upstream is   hours.


The time equation is


     = .


Cancel 11 in both sides


     = .


    2*(x-5) = x - 3


    2x - 10 = x - 3


    x = 10-3 = 7.


Answer.  The speed of the boat in still water is  7 miles per hour.


CHECK.  The spring time is   =  = 5.5 hours;


        The fall time is   =  = 2.75 hours.


        The spring time is twice the fall time.    ! Correct !