A project was completed in 30 days by teams A and B. Now team A worked alone for 24 days, and team B joined in. The two teams worked together for another 12 days. At this time, team A was transferred, and team B continued to work on it for 15 days. This project. How many days will it take Team A to do this project alone?
一项工程，甲、乙两队合做30天完成，现在甲队单独做24天后，乙队加入，两队又合做了12天，这时甲队调走，乙队继续做15天才完成这项工程．甲队单独做这项工程需多少天？
<gadget id="calculator">12 + 15</gadget>
<output>27</output>

<gadget id="calculator">27 / 30</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">24 - 15</gadget>
<output>9</output>

<gadget id="calculator">(1/10) / 9</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">1 / (1/90)</gadget>
<output>90</output>

<result>90</result>