Take 2 out of 6 different pairs of shoes, and there are no paired shoes. How many different ways are there in total?
从6双不同的鞋中取出2只，其中没有成双的鞋，共有多少种不同取法．
<gadget id="calculator">11 - 1</gadget>
<output>10</output>

<gadget id="calculator">6 * 10</gadget>
<output>60</output>

<result>60</result>