What is the product of the sum of 69 and 51 multiplied by their difference?
69与51的和乘以它们的差，积是多少．
<gadget id="calculator">69 + 51</gadget>
<output>120</output>

<gadget id="calculator">69 - 51</gadget>
<output>18</output>

<gadget id="calculator">120 * 18</gadget>
<output>2_160</output>

<result>2_160</result>