<PRE><B>Question 331852</B>
downstream:  Boat speed + current speed = total speed downstream =20/3 (distance/time)
--
so B+C=20/3
--
upstream:  Boat speed - current speed = total speed upstream =20/4 (distance/time)
--
so B-C=20/4=5

==
you have the solutions B=35/6, C=5/6
to check that these are in fact the solutions

just substitute these values into either B+C=20/3 or B-C=5 and see if left side of the equation equals the right side</PRE>