The master and apprentice work together to process 330 parts, the apprentice processes 20 parts per hour, and the master processes 15 more parts per hour than the apprentice. How many hours did the two work together to complete the task?
师徒二人共同加工零件330个，徒弟每小时加工20个，师傅每小时比徒弟多加工15个．两人合作几小时完成任务？
<gadget id="calculator">20 + 20 + 15</gadget>
<output>55</output>

<gadget id="calculator">330 / 55</gadget>
<output>6</output>

<result>6</result>