It is known that the sum of the minuend, the subtrahend and the difference is 15.5, and the minuend is 2.5 times the subtrahend, what is the difference.
已知被减数、减数与差的和是15.5，被减数是减数的2.5倍，差是多少．
<gadget id="calculator">15.5 / 2</gadget>
<output>7.75</output>

<gadget id="calculator">7.75 / 2.5</gadget>
<output>3.1</output>

<gadget id="calculator">7.75 - 3.1</gadget>
<output>4.65</output>

<result>4.65</result>