The sum of the minuend, the subtrahend and the difference is 180, the subtrahend is 50, what is the difference
被减数、减数与差的和是180，减数是50，差是多少
<gadget id="calculator">180 / 2</gadget>
<output>90</output>

<gadget id="calculator">90 - 50</gadget>
<output>40</output>

<result>40</result>