Xiao Ming plans to finish a chapter of exercises within a few days. If he does 5 questions a day, he will finish it exactly 1 day in advance. If he does 7 questions a day, he will finish it exactly 3 days in advance. How many questions are there in this chapter?
小明计划在若干天内做完一章习题，如果每天做5道题，恰好提前1天做完，如果每天做7道题，恰好提前3天做完．这章习题一共有多少道题？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<gadget id="calculator">7 * 5</gadget>
<output>35</output>

<result>35</result>