What is the difference between 3.5 and 1.8 plus 2.9?
3.5与1.8的差再加上2.9，和是多少？
<gadget id="calculator">3.5 - 1.8</gadget>
<output>1.7</output>

<gadget id="calculator">1.7 + 2.9</gadget>
<output>4.6</output>

<result>4.6</result>