The price of the skirt is twice that of the shoes, and the price of the top is three times that of the shoes. My mother bought a pair of shoes and a top for Xiaojuan. The total cost was 120 yuan. How much is a pair of shoes?
裙子的价钱是鞋的2倍，上衣的价钱是鞋的3倍，妈妈为小娟买了一双鞋和一件上衣，一共花了120元，一双鞋多少钱？
<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">120 / 4</gadget>
<output>30</output>

<result>30</result>