The two masters and apprentices process a batch of parts. The number of parts made by the master in 2 hours and the apprentice will take 3 hours. The apprentice will make 18 parts per hour. The two masters and apprentices process at the same time and finish the work in 12 hours. How many parts are there in this batch?
师徒二人加工一批零件，师傅2小时做的零件数徒弟要做3小时，徒弟每小时做18个零件，师徒二人同时加工经过12小时完工，这批零件有多少个？
<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">18 * (3/2)</gadget>
<output>27</output>

<gadget id="calculator">27 + 18</gadget>
<output>45</output>

<gadget id="calculator">45 * 12</gadget>
<output>540</output>

<result>540</result>