prozzy

the answer is -$97 for sure. 4 s1 q5 u' T  F- r( {: ^9 e
Think about it this way
3 H7 h* ~5 e1 Z4 U) j( |公仔箱論壇1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
$ j* Q8 j# `- W2 c6 e2 q5.39.217.762) Now, the owner discovered that the 100 bucks is fake. You can think this as a lost of $100. therefore the overall gain is $3-$100 = -$97