Mouth*2.5-2.3=4.7, what number should be filled in the mouth.
口*2.5-2.3=4.7，口中应填的数是多少．
<gadget id="calculator">4.7 + 2.3</gadget>
<output>7</output>

<gadget id="calculator">7 / 2.5</gadget>
<output>2.8</output>

<result>2.8</result>