There are 39 girls participating in the performance, which is 17 less than twice the number of boys. How many boys are in the show?
参加表演的女生有39人，比男生的2倍少17人．男生有多少人参加表演？
<gadget id="calculator">39 + 17</gadget>
<output>56</output>

<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<result>28</result>