Taking Mingming's home as the starting point, going east is positive, and going west is negative. If Mingming walks 30 meters west from home and then 40 meters east, what is the distance in meters from home?
以明明家为起点，向东走为正，向西走为负．如果明明从家先向西走30米，再向东走40米，这时明明离家的距离是多少米．
<gadget id="calculator">(-30) + 40</gadget>
<output>10</output>

<result>10</result>