When adding two numbers, one addend is increased by 0.9, the other is decreased by 1.4, and how much is the decrease
两个数相加，一个加数增加0.9，另一个加数减少1.4，和减少多少
<gadget id="calculator">1.4 - 0.9</gadget>
<output>0.5</output>

<result>0.5</result>