Answer:
I think it's 34
Step-by-step explanation:
cuz you add 11 and 12 frequency
1 is greater because it's not negative
Recall your d = rt, distance = rate * time.
let's say the boat has a still water rate of "b", and the current has a a rate of "c", ok.... when the boat is going upstream, is not really going "b" fast, is going slower at "b - c", due to the current going in the opposite direction.
when the boat is coming downstream, is not going "b" fast either, is going faster, is going "b + c", due to the current adding speed to it.
we know the trip up was 108 kms, thus the return trip is also 108 kms.

and surely you know how much that is.
what's the boat's speed? well, 36 + c = b.
Easy peasy lemon squeesy :D (-.-)! more blueberries! omgydnkhtdt(Oh my god you do not know how to do this