Asked to calculate a-(bc), Xiaoqiang calculated it as abc, and the result was 40 less than the correct answer. Then c= how much.
要求计算a-(b-c)，小强却把它算成了a-b-c，结果比正确答案小40．那么c=多少．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<result>20</result>