In a subtraction formula, the sum of the minuend, the subtrahend and the difference is 128, and the difference is 3 times the subtrahend. What is the difference?
在一道减法算式里，被减数、减数与差这三个数的和是128，差是减数的3倍．求差是多少？
<gadget id="calculator">1 + 3 + 1 + 3</gadget>
<output>8</output>

<gadget id="calculator">128 / 8</gadget>
<output>16</output>

<gadget id="calculator">3 * 16</gadget>
<output>48</output>

<result>48</result>