The students participated in the summer camp, 21 people from the lower grades participated in the summer camp, and 11 times the number of students from the upper grades participated in the summer camp than the lower grades. How many more people in the upper grades attend summer camp than in the lower grades?
同学们参加暑期夏令营，低年级参加夏令营的有21人，高年级参加夏令营的人数是低年级的11倍．高年级参加夏令营的人数比低年级多多少人？
<gadget id="calculator">11 - 1</gadget>
<output>10</output>

<gadget id="calculator">21 * 10</gadget>
<output>210</output>

<result>210</result>