In the subtraction formula, the difference is 0.8, the sum of the minuend, the subtrahend and the difference is 4, what is the subtrahend.
在减法算式中，差是0.8，被减数、减数、差的和是4，减数是多少．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 - 0.8</gadget>
<output>1.2</output>

<result>1.2</result>