The store stipulates that 7 empty bottles can be exchanged for 1 bottle of Coke. If you want to drink 100 bottles of Coke, you only need to buy how many bottles.
商店规定7个空瓶可换1瓶可乐，要喝100瓶可乐，只需购买多少瓶．
<gadget id="calculator">7 * 12</gadget>
<output>84</output>

<gadget id="calculator">84 + 12</gadget>
<output>96</output>

<gadget id="calculator">100 - 96</gadget>
<output>4</output>

<gadget id="calculator">84 + 4</gadget>
<output>88</output>

<result>88</result>