There are 10 digital cards "3", "4", and "5" each, and 8 of them are randomly selected. The sum of their numbers is 31, and how many cards are at most "3".
数字卡片"3"、"4"、"5"各10张，从中任意选出8张，它们的数字和是31，则最多有多少张是卡片"3"．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<result>4</result>