If going south is positive and going north is negative, Xiao Liang starts from the school gate, goes southward for 300 meters, then goes northward for 200 meters, how many meters is he at the south of the school gate?
如果向南为正，向北为负，小亮以校门为起点，先向南行300米，接着向北行200米，这时他在校门南多少米
<gadget id="calculator">300 - 200</gadget>
<output>100</output>

<result>100</result>