A bottle of Coke is 2.5 yuan, 3 empty bottles can be exchanged for another bottle of Coke, there is 30 yuan, how many bottles of Coke can you drink at most.
一瓶可乐2.5元，3个空瓶可以再换一瓶可乐，有30元，最多可以喝到多少瓶可乐．
<gadget id="calculator">30 / 2.5</gadget>
<output>12</output>

<gadget id="calculator">12 + 4 + 1 + 1</gadget>
<output>18</output>

<result>18</result>