If the altitude of A is +7 meters, and the altitude of B is -3 meters, what is the difference in height between A and B?
如果A地海拔高度是+7米，B地海拔高度是-3米，A、B两地高度相差多少米．
<gadget id="calculator">7 - (-3)</gadget>
<output>10</output>

<result>10</result>