For a batch of parts, A can make 60 pieces a day, and B can make 50 pieces a day. If A can do it alone, it can be completed in 15 days. How many days can it be completed if B is asked to do it alone?
一批零件，甲每天能做60个，乙每天可做50个，如果让甲单独做，15天可完成．如果让乙单独做，多少天可以完成？
<gadget id="calculator">15 / 50</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">60 * (3/10)</gadget>
<output>18</output>

<result>18</result>