Zhang Qiang bought a coat, a hat and a pair of shoes for 270 yuan. The coat was 140 yuan more expensive than the shoes, and the coat and shoes cost 210 yuan more than the hat. How much did Zhang Qiang spend on the pair of shoes?
张强用270元买了一件外衣，一顶帽子和一双鞋子，外衣比鞋贵140元，买外衣和鞋比帽子多花210元，张强买这双鞋花了多少钱？
<gadget id="calculator">270 + 210</gadget>
<output>480</output>

<gadget id="calculator">480 / 2</gadget>
<output>240</output>

<gadget id="calculator">240 - 140</gadget>
<output>100</output>

<gadget id="calculator">100 / 2</gadget>
<output>50</output>

<result>50</result>