If you sell a pair of shoes for 135 yuan, you can earn 35%, what is the purchase price?
一双鞋子如果卖135元，可以赚35%，则进价是多少元．
<gadget id="calculator">35 / 100</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">1 + (7/20)</gadget>
<output>27/20 = around 1.35</output>

<gadget id="calculator">135 / (27/20)</gadget>
<output>100</output>

<result>100</result>