There are three kinds of cups with unit prices of 3 yuan, 4 yuan, and 6 yuan in the mall. Mom asked Xiao Ming to buy cups, at least one of each kind of cup. Xiao Ming pays 30 yuan, gets back 5 yuan, how many cups Xiao Ming can buy at most 3 yuan.
商场里有三种单价分别是3元、4元、6元的杯子．妈妈让小明去买杯子，每种杯子至少要买一个．小明付款30元，找回5元，小明最多可以买多少个3元的杯子．
<gadget id="calculator">30 - 5</gadget>
<output>25</output>

<gadget id="calculator">25 - 4 - 6</gadget>
<output>15</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<result>5</result>