Hongshan Elementary School organizes students to participate in the district sports meeting. There are 12 students in the fourth grade, 7 students less than the fifth grade, and the number of students in the sixth grade is three times the total number of participants in the fourth and fifth grades. How many people in 6th grade attend?
红山小学组织学生参加区运动会，四年级有12人参加，比五年级少7人，六年级参加的人数是四五年级参加的总人数的3倍．六年级有多少人参加？
<gadget id="calculator">12 + 7 + 12</gadget>
<output>31</output>

<gadget id="calculator">31 * 3</gadget>
<output>93</output>

<result>93</result>