If my mother rides a bicycle both to work and after get off work, it will take a total of 40 minutes on the road; if she rides a bicycle to work and walks after get off work, it will take a total of 55 minutes on the road. If she walks back and forth, how many minutes will it take on the journey?
如果妈妈上班、下班都骑车，路上一共要用40分钟；如果上班时骑车，下班时步行，路上一共要用55分钟．如果她往返都步行，路上一共要用多少分钟．
<gadget id="calculator">55 * 2</gadget>
<output>110</output>

<gadget id="calculator">110 - 40</gadget>
<output>70</output>

<result>70</result>