Its a sign convention error. As far as the manager is concerned, he HAS $25 dollars.
As far as the guys are concerened they GAVE 9 dollars.
Here's the crux. The boy TOOK 2 dollars.
Therefore the equation is:
9*3 - 2 = 25.
Want to make the above trick even worse?
Have those men give their three dollars back.
That way they each paid 9*3 + 3. which adds up to thirty. But then where did the boy's two dollars come from?!?! Its the PERPETUAL MONEY MACHINE!!!