It takes 75 minutes for Xiaoliang to go to school by car, and it takes 75 minutes to walk home after school. If it only takes 30 minutes to go back and forth by car, how many minutes does it take for Xiaoliang to walk back and forth.
小亮乘车到学校上课，放学后步行回家共需要75分钟，如果来回乘车只要30分钟，那么小亮往返都步行要多少分钟．
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">75 - 15</gadget>
<output>60</output>

<gadget id="calculator">60 * 2</gadget>
<output>120</output>

<result>120</result>