There are 5 balls of the same size in red, yellow, and blue mixed together, at least how many balls must be drawn to ensure that 2 red balls are drawn.
有红、黄、蓝三种颜色同样大小的球各5个混在一起，至少要摸出多少个才能保证摸出2个红球．
<gadget id="calculator">5 + 5 + 2</gadget>
<output>12</output>

<result>12</result>