To build a road with a length of 153.9 kilometers, if team A builds 3.6 kilometers every day, team B builds 4.5 kilometers every day. How many days can the two teams complete the task together?
要修一条长153.9千米的公路，如果甲队每天修3.6千米，乙队每天修4.5千米．两队合修多少天能完成任务？
<gadget id="calculator">3.6 + 4.5</gadget>
<output>8.1</output>

<gadget id="calculator">153.9 / 8.1</gadget>
<output>19</output>

<result>19</result>