Everyone in Class 1 of the fifth grade participated in at least one interest group, 45 people participated in the Chinese interest group, 37 people participated in the mathematics interest group, and 20 people participated in both groups. How many people are there in this class?
五年级1班每人都至少参加一个兴趣小组，参加语文兴趣小组的有45人，参加数学兴趣小组的有37人，有20人两个小组都参加．这个班共有多少人．
<gadget id="calculator">37 - 20</gadget>
<output>17</output>

<gadget id="calculator">45 + 17</gadget>
<output>62</output>

<result>62</result>