Zhang Hong went from her home to her good friend Li Yue's to play. If you take the car back and forth, it will take 30 minutes on the road. If you go by car and walk back, it will take 50 minutes. So how many minutes does it take for Zhang Hong to walk from home to Li Yue's home?
张红从自己家到好朋友李悦家去玩．如果来回都乘车，那么路上将要用去30分钟．如果去时乘车，回来时步行，那么将要用去50分钟．那么张红从家步行到李悦家需要多少分钟？
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">50 - 15</gadget>
<output>35</output>

<result>35</result>