+50 meters means that it is 50 meters south of the school. If Fangfang walks 320 meters south from the school and then 400 meters north, how many meters can Fangfang's position be expressed at this time?
+50米表示在学校南面50米处，若芳芳从学校先向南走320米，再向北走400米，则芳芳这时的位置可以表示为多少米．
<gadget id="calculator">400 - 320</gadget>
<output>80</output>

<result>80</result>