A piece of cloth can be used to make 12 sets of clothing. If this piece of cloth is only used as a jacket, it can be made into 20 pieces. If this piece of cloth is only used as a pair of pants, how many sets can be made.
一块布可以做12套服装，如果这块布只做上衣可以做20件，如果这块布只做裤子可以做多少条．
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/12) - (1/20)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<result>30</result>