Xiao Ming takes home as the starting point, eastward is positive, and westward is negative. Xiao Ming walked +30 meters eastward from home, and then -30 meters westward. At this time, how many meters is Xiao Ming away from home?
小明以家为起点，向东为正，向西为负．小明从家向东走了+30米，又向西走了-30米．这时小明离家多少米．
<gadget id="calculator">30 + (-30)</gadget>
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