Solution to Bjorn's question.

The question.

Since no one is willing to post their solutions, I will reveal the answers.

Read carefully, your Guru speaks!

Firstly, the calculation is erroneous. I am using a counter-example,

You should not do 3 x $9 + $2 = $29.
What if the owner gave back $10 and the bellboy pocketed $1, leaving $9 to be shared among the three? Each will get $3 back, hence each paid only $7.
3 x $7 + $1 = $22. What happened to the $8?

In fact, we should look at only the cost of the room.
In the original question, the room cost $25. $25 = 3 x $9 - $2 (each paid $9 and $25 goes to the room, $2 to the bellboy)

In my counter example, the room cost $20. $20 = 3 x $7 - $1

See?