A has 20 books, B has 3 times as many books as A, and 5 times as many as C. How many books does C have?
甲有20本书，乙的书的本数既是甲的3倍，又是丙的5倍．丙有多少本书．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">20 * (3/5)</gadget>
<output>12</output>

<result>12</result>