In a subtraction formula, the sum of the minuend, the subtrahend and the difference is 120, the subtrahend is the difference (1/3), what is the subtrahend.
在一道减法算式中，被减数、减数与差的和为120，减数是差的(1/3)，减数是多少．
<gadget id="calculator">120 / 2</gadget>
<output>60</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">60 / 4</gadget>
<output>15</output>

<gadget id="calculator">15 * 1</gadget>
<output>15</output>

<result>15</result>