(3/5) of a box of pens is exactly 15. How many pens are there in this box?
一盒钢笔的(3/5)正好是15枝，这盒钢笔共有多少枝．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">15 / (3/5)</gadget>
<output>25</output>

<result>25</result>