The school held a group gymnastics performance. There were 42 participants in the fifth grade, and the number of participants in the sixth grade was 15 less than twice that of the fifth grade. How many people participated in the sixth grade?
学校进行团体操表演，五年级有42人参加，六年级参加的人数比五年级的2倍少15人，六年级有多少人参加？
<gadget id="calculator">42 * 2</gadget>
<output>84</output>

<gadget id="calculator">84 - 15</gadget>
<output>69</output>

<result>69</result>