4.5 times a number minus 0.8 times 2.5, the difference is 2.5, what is this number?
一个数的4.5倍减去2.5的0.8倍，差是2.5，这个数是多少？
<gadget id="calculator">2.5 * 0.8</gadget>
<output>2</output>

<gadget id="calculator">2 + 2.5</gadget>
<output>4.5</output>

<gadget id="calculator">4.5 / 4.5</gadget>
<output>1</output>

<result>1</result>