The Monkey King Sun Wukong held a group meeting of monkeys. During the roll call, he found that the number of absent monkeys was the number of attendees (3/7). Just about to get angry, another 5 monkeys came. At this time, the number of absent monkeys was the number of attendees ( 7/13), how many monkeys are there in this group?
美猴王孙悟空召开群猴会，点名时发现缺席的只数是出席只数的(3/7)，刚要发火，又跑来5只猴子，这时缺席的只数是出席只数的(7/13)，请问这群猴子有多少只？
<gadget id="calculator">7 / 20</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(7/20) - (3/10)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">5 / (1/20)</gadget>
<output>100</output>

<result>100</result>