In a test, Xiaoming answered 10 questions wrongly, Xiaogang answered 8 questions wrongly, the number of questions answered correctly by Xiaoqiang was equal to the sum of the number of questions answered correctly by Xiaoming and Xiaogang, and Xiaoqiang answered 3 questions wrongly. How many questions are there in this test?
一次测验中，小明答错了10道题，小刚答错了8道题，小强答对的题的数量等于小明与小刚答对题的数量之和，且小强答错了3道题．这次测验共有多少道题．
<gadget id="calculator">8 - 3</gadget>
<output>5</output>

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

<gadget id="calculator">1 - 1</gadget>
<output>0</output>

<gadget id="calculator">1 + 0</gadget>
<output>1</output>

<gadget id="calculator">15 / 1</gadget>
<output>15</output>

<result>15</result>