+30 means 30 meters north of the school. If you walk 350 meters south from the school and then 280 meters north, how many meters can you express the position at this time?
+30表示在学校北面30米处，若明明从学校先向南走350米，再向北走280米，则明明这时的位置可以表示为多少米．
<gadget id="calculator">350 - 280</gadget>
<output>70</output>

<result>70</result>