What is the product of the sum of 12.9 and 7.5 multiplied by their difference?
12.9与7.5的和与它们的差相乘，积是多少？
<gadget id="calculator">12.9 + 7.5</gadget>
<output>20.4</output>

<gadget id="calculator">12.9 - 7.5</gadget>
<output>5.4</output>

<gadget id="calculator">20.4 * 5.4</gadget>
<output>110.16</output>

<result>110.16</result>