If a number is 28 less than 56, what is the average of this number and 56?
一个数比56少28，则这个数与56的平均数是多少．
<gadget id="calculator">56 - 28</gadget>
<output>28</output>

<gadget id="calculator">28 + 56</gadget>
<output>84</output>

<gadget id="calculator">84 / 2</gadget>
<output>42</output>

<result>42</result>