I believe this is a brain teaser im trying to solve

Question

A $100 is taken from my register without my knowledge. The person comes back 5 minutes later with the same $100 and spends $70 on items an given $30 in change. How much money did i lose?

Answer 1

I agree with Mark. The second transaction, whether it is by the same person or another customer does, not represent a loss. It is just a simple sale of merchandise for $70. You lost the $100 stolen.

Answer 2

Although you got the $100 back you gave out $70 in goods and $30 in change. You are still out $100.

Answer 3

Your total outlay in $ was 100 (stolen) plus $30 (paid out in change); you received $70 but that can be considered as negated by the handover of merchandise of equivalent value (disregarding any 'profit' in this unfortunate exchange).