Master Zhang processed a batch of parts, and completed (1/3) of this batch of parts on the first day. If he processed 15 more parts, he could complete half of this batch of parts. How many parts are there in total?
张师傅加工一批零件，第一天完成了这批零件的(1/3)，如果再加工15个，就可以完成这批零件的一半，这批零件共有多少个？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/2) - (1/3)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">15 / (1/6)</gadget>
<output>90</output>

<result>90</result>