The teacher and the apprentice start working at the same time to make machine parts. The apprentice's task is the master's (3/4). The master does 90 per hour, and the apprentice does 60 per hour. When the apprentice completes the task, the master can exceed 120. How many processing tasks does the master have?
师、徒二人同时开工做机器零件．徒弟的任务是师傅的(3/4)，师傅每小时做90个，徒弟每小时做60个，到徒弟完成任务时，师傅能超额120个，师傅的加工任务是多少个？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">120 * (3/4)</gadget>
<output>90</output>

<gadget id="calculator">90 * (3/4)</gadget>
<output>135/2 = around 67.5</output>

<gadget id="calculator">(135/2) - 60</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">90 / (15/2)</gadget>
<output>12</output>

<gadget id="calculator">60 * 12</gadget>
<output>720</output>

<gadget id="calculator">720 / (3/4)</gadget>
<output>960</output>

<result>960</result>