To complete a batch of parts, the master takes 28 hours to complete, and the apprentice takes 5 hours less than twice as much as the master. How many hours does the apprentice take to complete?
完成一批零件，师傅用28个小时完成，徒弟用的时间比师傅的2倍少5个小时，徒弟用多少小时完成？
<gadget id="calculator">28 * 2</gadget>
<output>56</output>

<gadget id="calculator">56 - 5</gadget>
<output>51</output>

<result>51</result>