prozzy

the answer is -$97 for sure.
0 O' K: C  U8 ~4 k- g( |5 M! `TVBNOW 含有熱門話題，最新最快電視，軟體，遊戲，電影，動漫及日常生活及興趣交流等資訊。Think about it this way 公仔箱論壇5 Y8 y- t1 }) m% {% @
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)# J  \! S1 K, u, p
2) 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