When adding two numbers, one addend is increased by 1.2, the other is decreased by 0.7, and how much is the increase
两个数相加，一个加数增加1.2，另一个减少0.7，和增加多少
<gadget id="calculator">1.2 - 0.7</gadget>
<output>0.5</output>

<result>0.5</result>