25.6 minus twice a number, the difference is 1.3, find this number.
25.6减去一个数的2倍，差是1.3，求这个数．
<gadget id="calculator">25.6 - 1.3</gadget>
<output>24.3</output>

<gadget id="calculator">24.3 / 2</gadget>
<output>12.15</output>

<result>12.15</result>