Calculate with a simple method: 1968+1978-1988+1998-2008.
用简便方法计算：1968+1978-1988+1998-2008．
<gadget id="calculator">1_978 - 1_988</gadget>
<output>-10</output>

<gadget id="calculator">1_998 - 2_008</gadget>
<output>-10</output>

<gadget id="calculator">1_968 + (-10) + (-10)</gadget>
<output>1_948</output>

<result>1_948</result>