Your problem is imaginary. The issue you project is combining addition with subtraction to come up with the discrepancy. Simply, addition to addition, 25 bucks + 3 bucks (1 for each person who paid the original amount) + 2 bucks that the bell-hop kept = the 30 bucks that was the originally paid amount.
I can get to 11 fingers on my hands with the same combination of addition subtraction. First hand - count - 1,2,3,4,5. Second hand - reverse - 10,9,8,7,6. Now add the last digits and “Bingo” 5 + 6 = 11 fingers.
you just shot the wind out of my saddle..next you’re probably going to call me when I mix metaphors.