There is a batch of parts that can be processed by both lathes A and B. If A lathe is processed alone, it can complete the task 10 days earlier than B lathe alone. Now use two lathes A and B to process together, and the task is completed in 12 days. How many days will it take to complete the task if only A lathe is used for processing alone?
有一批零件，甲、乙两种车床都可以加工．如果甲车床单独加工，可以比乙车床单独加工提前10天完成任务．现在用甲、乙两车床一起加工，结果12天就完成了任务．如果只用甲车床单独加工需多少天完成任务？
<gadget id="calculator">12 / 1</gadget>
<output>12</output>

<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<result>20</result>