Melody

answered 

Here go.

6 from the first corner, there will be 4 more from the second vertex and another 2 from the last one.

The circle in the middle goes through more than 4 so that does not fit the requirements.

Maybe you should try using my method.

I have never had a problem.

I did not mean it was a simple question.

I did not think it was simple at all.

I just meant that 3*5=15 seemed very coincidental.  I was not completely sure if my answer was correct.

I do not think there is enough information ....   Unless you mean that they are just going to float downstream from one to the other?

In which case I think it will take 15 hours to get from one to the other.   ... maybe....  Sounds a bit too simple .... 

If Schäl weighs 70 kg plus half my weight then 70kg must BE half my weight.

Also wiegt Schäl hundertvierzig kg.

Travisio,

Your graph shows that the funtion is symmetrical about the y axis

this means that f(x)=f(-x)

and that means that the function is even

Do you understand now?

Yes I understood that.  :)

Next time you can send me a message and ask me to unlock it.

You can still write a new post but put an easy to use link and ask people to do the actual answer on the original post.

They can also put a comment on the new post saying that they have added an answer.

It is a bit of a rigmarole, sorry about that, but I do not see a better way.

I'd like to try it with other similar questions.

It looks like an easy way that would not normally require a lot of trial and error, just a bit I think.