The master and the apprentice work together to process a batch of parts, the apprentice processed 25 parts, and the master processed 6 parts three times less than the apprentice. How many pieces did the master process?
师徒两人共同加工一批零件，徒弟加工了25个，师傅加工的比徒弟的3倍少6个．师傅加工了多少个？
<gadget id="calculator">25 * 3</gadget>
<output>75</output>

<gadget id="calculator">75 - 6</gadget>
<output>69</output>

<result>69</result>