So, when you travel with the current, the current speed adds to your still water speed. Travelling upstream, it subracts from it.
If I can row 5 mph and the current is 2 mph, I'm going to go 7 mph downstream and 3 mph back upstream.
d = rt
264 = 11(b + c)
264 = 33(b - c)
Now, we can multiply out 11 and 33, orrrrr, since 11 and 33 qre factors on the right, we can divide both sides by 11 and 33, respectively.
24 = b + c
8 = b - c
Adding the two together.
32 = 2b
b = 16 mph
Therest is on you.