Mom buys tableware with a sum of money. If she buys only bowls, she can buy 20 sets, and if she buys only chopsticks, she can buy 60 pairs. Now consider a bowl and a pair of chopsticks as a set. How many sets can this money buy?
妈妈用一笔钱买餐具，如果单买碗可以买20个，单买筷子可以买60双，现在把一个碗和一双筷子看做一套，这笔钱可以买多少套？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/20) + (1/60)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / (1/15)</gadget>
<output>15</output>

<result>15</result>