A certain unit plans to hold a football match in the Lunjiao Stadium, and plans to give away 5% of the tickets for free, and give away 42 tickets for free. How many seats are there in the Lunjiao Stadium?
某单位计划在伦教体育馆举行足球赛，计划把5%的门票免费送出，免费送出门票42张，伦教体育馆共有多少个座位？
<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">42 / (1/20)</gadget>
<output>840</output>

<result>840</result>