The teacher and the apprentice work together to make 264 parts. The apprentice first works for 4 hours and then cooperates with the master for 8 hours to complete the task. It is known that the apprentice makes 3 fewer parts per hour than the master, and how many parts the master makes per hour.
师、徒二人合做264个零件，徒弟先做4小时又和师傅合做了8小时才完成任务，已知徒弟每小时比师傅少做3个，师傅每小时做多少个零件．
<gadget id="calculator">3 * 8</gadget>
<output>24</output>

<gadget id="calculator">264 - 24</gadget>
<output>240</output>

<gadget id="calculator">4 + 8 + 8</gadget>
<output>20</output>

<gadget id="calculator">240 / 20</gadget>
<output>12</output>

<gadget id="calculator">12 + 3</gadget>
<output>15</output>

<result>15</result>