Master Ma and Master Zhang worked together to process a batch of parts. It was originally planned that Master Ma processed 8 more parts than Master Zhang every day, and it took 15 days to complete. In order to catch up with Master Ma’s efficiency, Master Zhang called an apprentice to help him from the very beginning. As a result, the master and apprentice processed 4 more parts every day than Master Ma did. It took 12 days to complete the work, so how much did Master Ma process every day? parts?
马师傅和张师傅合伙加工一批零件，原计划马师傅每天比张师傅多加工8个零件，共用了15天完成．张师傅为了赶上马师傅的效率，叫了一个徒弟从一开始就来帮忙，结果师徒俩每天反比马师傅还多加工4个零件，这样用了12天就完成了，那么马师傅每天加工多少个零件？
<gadget id="calculator">8 + 4</gadget>
<output>12</output>

<gadget id="calculator">60 / 12</gadget>
<output>5</output>

<gadget id="calculator">60 / 15</gadget>
<output>4</output>

<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<gadget id="calculator">12 * 1 * 4</gadget>
<output>48</output>

<gadget id="calculator">48 + 8</gadget>
<output>56</output>

<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<result>28</result>