okay I have had to make some assumptions here whivhis never great when answering maths questions.
1) I have assumed that a couple is 2. So there are 3 people and 1 canoe.
2) I have assumed that they all hired vest at $2 each and this was a one off cost, not an hourly cost.
so
Let the numberof hours be x
5x+(3*2)=41
5x+6=41
5x=35
x=7 hours