The scammer went to the store to buy something worth 9 yuan with 100 yuan banknotes, and the salesperson gave him 91 yuan. At this time, he claimed that he had some change, gave the salesperson 9 yuan and asked for his original 100 yuan back. So, how much did he cheat the store?
骗子到商店用100元面值的钞票买9元的东西，售货员找给他91元．这时，他又称自己己有零钱，给了售货员9元而要回了自己原来的100元．那么，他骗了商店多少元．
<gadget id="calculator">91 - 9</gadget>
<output>82</output>

<gadget id="calculator">82 + 9</gadget>
<output>91</output>

<result>91</result>