It takes Xiaogang 36 minutes to walk from home to school, and 12 minutes to ride a bicycle. Today, when he rode his bicycle from home for 8 minutes, the car broke down and he had to walk to school. How many minutes did Xiao Gang walk for?
小刚从家到学校，步行需要36分钟，骑自行车需要12分钟．今天当他骑自行车从家出发8分钟后，车子坏了，只好步行到学校．小刚步行了多少分钟？
<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<result>12</result>