What is half of the sum obtained by subtracting 18 from 542 and adding 12?
542减去18的差，再加上12所得的和的一半是多少
<gadget id="calculator">542 - 18</gadget>
<output>524</output>

<gadget id="calculator">524 + 12</gadget>
<output>536</output>

<gadget id="calculator">536 / 2</gadget>
<output>268</output>

<result>268</result>