Three students share exercise books, A gets 5 less than half of the total, B gets 2 more than the remaining half, and C gets 12, how many exercise books are there in total?
三个同学分练习本，甲得到的比总数的一半少5本，乙得到的比余下的一半多2本，丙得到12本，求共有练习本多少本？
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">12 - 5</gadget>
<output>7</output>

<gadget id="calculator">6 + 2 + 7</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>