In a formula, the sum of the minuend, the subtrahend and the difference is 240, and the subtrahend is twice the difference, what is the subtrahend?
在一个算式中，被减数、减数与差的和是240，而且减数是差的2倍，减数是多少？
<gadget id="calculator">1 + 2 + 2 + 1</gadget>
<output>6</output>

<gadget id="calculator">240 / 6</gadget>
<output>40</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<result>80</result>