Cong Cong's father left early one day, took the bus that picked him up half an hour later, and then took the bus to the company. He arrived at the company 10 minutes earlier than usual. How much time earlier than usual did he leave the house?
聪聪的爸爸有一天提前出门，半小时后坐上了接他的班车，然后乘车去公司，比平时早10分钟到公司，他比平时提前多少时间出门？
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 + 30</gadget>
<output>35</output>

<result>35</result>