Question 382935
Let x=amount of time it takes to clean the whole boat
Let's first find our rate of work e.g. the amount of boat that we can clean per hour.
If it takes 5 hrs to clean 2/3 boat, then in 1 hour we can clean 2/15(2/3 divided by 5) of the boat so we clean at the rate of 2/15 boat per hour
Now our equation to solve is:
(2/15)x=1 (1 boat, that is) multiply each side by 15
2x=15
x=7 1/2 hours 

Another way to look at this problem is as follows:
In 2 1/2 hours we can clean 1/3 of the boat
3*(1/3)=whole boat and that would take 3* (2 1/2) hours=7 1/2 hours
Hope this helps---ptaylor