There is a job. After 12 days of cooperation between Ao Zema and Ou Ou, there is still a part of the work that has not been completed. If it takes 15 days for Ao Zema to complete the remaining work alone, and it takes 20 days for Ou Ou to complete, then, How many days will it take for all this work to be done by Ozebra?
有一份工作，奥斑马与欧欧两人合作了12天后，还剩下一部分工作没有完成，如果将剩下的工作由奥斑马单独完成需要15天，而由欧欧完成需要20天，那么，这件工作全部由奥斑马完成需要多少天？
<gadget id="calculator">15 / 20</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">12 * (3/4)</gadget>
<output>9</output>

<gadget id="calculator">9 + 12 + 15</gadget>
<output>36</output>

<result>36</result>