Students who get A grades in writing can exchange 10 A's for 3 award cards. Xiaoxiao now has 12 award cards. How many A's did she exchange for? Please use proportion knowledge to answer.
凡是书写得A等的同学可以用10个A换取3张奖卡，笑笑现在有12张奖卡，她是用几个A换的？请用比例知识解答．
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">12 / (3/10)</gadget>
<output>40</output>

<result>40</result>