In a subtraction formula, the sum of the minuend, the subtrahend and the difference is 960, and the subtrahend is 40 greater than the difference. Find the subtrahend.
在一个减法算式里，被减数、减数与差这三个数的和是960，减数比差大40，求减数．
<gadget id="calculator">960 / 2</gadget>
<output>480</output>

<gadget id="calculator">480 + 40</gadget>
<output>520</output>

<gadget id="calculator">520 / 2</gadget>
<output>260</output>

<result>260</result>