The altitude of A is -180 meters, and the altitude of B is -160 meters. Compared with the two places, how much is A lower than B?
甲处海拔-180米，乙处海拔-160米，两处相比，甲比乙低多少米．
<gadget id="calculator">(-160) - (-180)</gadget>
<output>20</output>

<result>20</result>