Can't check the formula of 679+539=1218
不能验算679+539=1218的算式是多少
<gadget id="calculator">539 - 679</gadget>
<output>-140</output>

<gadget id="calculator">679 + (-140)</gadget>
<output>539</output>

<gadget id="calculator">679 - 539</gadget>
<output>140</output>

<result>140</result>