Three students from Chunfeng Elementary School participated in the mathematics competition. There were 10 questions in total. One correct answer was worth 10 points, and one wrong answer was deducted 3 points. All three students answered all the questions. Xiao Ming got 87 points and Xiao Hong got 74 points. , Xiaohua scored 9 points, how many questions did the three of them answer correctly?
春风小学3名云参加数学竞赛，共10道题，答对一道题得10分，答错一道题扣3分，这3名同学都回答了所有的题，小明得了87分，小红得了74分，小华得了9分，他们三人一共答对了多少道题．
<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<gadget id="calculator">100 - 87</gadget>
<output>13</output>

<gadget id="calculator">10 + 3</gadget>
<output>13</output>

<gadget id="calculator">13 / 13</gadget>
<output>1</output>

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">100 - 74</gadget>
<output>26</output>

<gadget id="calculator">26 / 13</gadget>
<output>2</output>

<gadget id="calculator">10 - 2</gadget>
<output>8</output>

<gadget id="calculator">100 - 9</gadget>
<output>91</output>

<gadget id="calculator">91 / 13</gadget>
<output>7</output>

<gadget id="calculator">10 - 7</gadget>
<output>3</output>

<gadget id="calculator">9 + 8 + 3</gadget>
<output>20</output>

<result>20</result>