From school to home, if you ride a bicycle for 3 minutes first, then walk for 15 minutes to get there; if you walk for 5 minutes first, then ride for 5 minutes to get there. How many minutes does it take to walk from home to school?
从学校到家，如果先骑车3分钟，再步行15分钟可到达；如果先步行5分钟，再骑车5分钟也可以到达．如果从家步行到学校需要多少分钟？
<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 + 15</gadget>
<output>30</output>

<result>30</result>