The school holds a knowledge contest. Each correct answer gets 10 points, and 5 points are deducted for each wrong answer (or non-answer). There are 12 questions in total. Xiao Ming scored 75 points and answered every question. How many questions did he answer wrong?
学校举行知识竞赛，每答对一题得10分，答错(或不答)一题倒扣5分，共有12题，小明得了75分，且每题都做了，他答错了多少题？
<gadget id="calculator">12 * 10</gadget>
<output>120</output>

<gadget id="calculator">120 - 75</gadget>
<output>45</output>

<gadget id="calculator">10 + 5</gadget>
<output>15</output>

<gadget id="calculator">45 / 15</gadget>
<output>3</output>

<result>3</result>