For a project, it takes 30 days for A to finish and 10 days for B to finish. During the process, A and B each asked for a few days off, of which B took 6 days. In the end, the two of them shared 13 days to complete the task, so A asked for leave. how many days?
一项工程，甲做完需要30天，乙做完需要10天，中途甲乙各请了几天假，其中乙请了6天，最终两人共用了13天完成这项任务，那么甲请了多少天？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">13 - 6</gadget>
<output>7</output>

<gadget id="calculator">(1/10) * 7</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(3/10) / (1/30)</gadget>
<output>9</output>

<gadget id="calculator">13 - 9</gadget>
<output>4</output>

<result>4</result>