Team A and Team B jointly repair a road with a length of 420 meters. Team A repairs 70 meters every week, and Team B repairs 3 times the length of Team A every week. If this road is repaired by Team B alone, how many weeks can it be completed?
甲、乙两队合修一条长420米的公路，甲队每周修70米，乙队每周修的长度是甲队的3倍．这条公路如果由乙队单独来修，几周可以修完？
<gadget id="calculator">70 * 3</gadget>
<output>210</output>

<gadget id="calculator">420 / 210</gadget>
<output>2</output>

<result>2</result>