project, Master Wang. Zhang master cooperation can be completed in 15 days. Master Wang will do it for 5 days first, and then Master Zhang will do it for 3 days to complete the workload (7/30). How many days will this project be done by Master Wang alone?
一项工程，王师傅．张师傅合作15天可以完成．先由王师傅做5天，再由张师傅接着做3天，完成工作量的(7/30)．这项工程如果由王师傅单独做多少天？
<gadget id="calculator">7 / 30</gadget>
<output>7/30 = around 0.233333</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/15) * 3</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(7/30) - (1/5)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">(1/30) / 2</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">1 / (1/60)</gadget>
<output>60</output>

<result>60</result>