In a subtraction formula, minuend + subtrahend + difference = 180, subtrahend - difference = 20, what is the difference?
在一道减法算式中，被减数+减数+差=180，减数-差=20，差是多少？
<gadget id="calculator">180 / 2</gadget>
<output>90</output>

<gadget id="calculator">90 + 20</gadget>
<output>110</output>

<gadget id="calculator">110 / 2</gadget>
<output>55</output>

<gadget id="calculator">55 - 20</gadget>
<output>35</output>

<result>35</result>