The master and apprentice jointly rented a batch of parts. The master made 5 hours and the apprentice made 8 hours, making a total of 284 parts. It is known that the number of parts made by the master in 3 hours is 12 more than that made by the apprentice in 4 hours. How many parts does the master make per hour on average?
师徒两人合租偶一批零件，师傅做了5小时，徒弟做了8小时，一共做了284个．已知师傅3小时做的零件数比徒弟4小时做的还多12个，师傅平均每小时做多少个零件？
<gadget id="calculator">8 / 4</gadget>
<output>2</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">284 + 24</gadget>
<output>308</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">5 + 6</gadget>
<output>11</output>

<gadget id="calculator">308 / 11</gadget>
<output>28</output>

<result>28</result>