Port A and port B are 1200 kilometers apart. Ship A travels from port A to port B at a speed of 60 kilometers per hour. 30 minutes after ship A leaves, ship B travels 70 kilometers per hour from port B to port A. How many hours after ship B leaves?
甲乙两港相距1200千米，甲船从甲港开往乙港，每小时行60千米．甲船开出30分钟后，乙船从乙港开往甲港每小时行70千米，乙船开出后几小时相遇？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">60 * (1/2)</gadget>
<output>30</output>

<gadget id="calculator">1_200 - 30</gadget>
<output>1_170</output>

<gadget id="calculator">60 + 70</gadget>
<output>130</output>

<gadget id="calculator">1_170 / 130</gadget>
<output>9</output>

<result>9</result>