For a project, if A does it on the first day, B on the second day, A on the third day, and B on the fourth day, so that they are done alternately, then it will be completed in an exact number of days; A does it, B does it on the third day, and A does it on the fourth day. In this way, they are done alternately, and the completion time will be half a day longer than the previous one. It is known that it takes 17 days for B to complete this project alone, how many days will it take for A to complete this project alone?
一项工程，第一天甲做，第二天乙做，第三天甲做，第四天乙做，这样交替轮流做，那么恰好用整数天完工；如果第一天乙做，第二天甲做，第三天乙做，第四天甲做，这样交替轮流做，那么完工时间要比前一种多半天．已知乙单独做这项工程需17天完成，甲单独做这项工程要多少天完成？
<gadget id="calculator">1 / 17</gadget>
<output>1/17 = around 0.058824</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/17) / (1/2)</gadget>
<output>2/17 = around 0.117647</output>

<gadget id="calculator">1 / (2/17)</gadget>
<output>17/2 = around 8.5</output>

<result>17/2 = around 8.5</result>