There are 300 students going for an autumn outing in 4 cars, each car has 78 seats, how many empty seats are there for students?
有300个同学乘4辆车去秋游，每辆车有78个座位，还有多少个空座位没有坐学生？
<gadget id="calculator">78 * 4</gadget>
<output>312</output>

<gadget id="calculator">312 - 300</gadget>
<output>12</output>

<result>12</result>