1. Party A can complete 1\3 and Party B can complete 1\6 every month, so the cooperation between Party A and Party B is 1\2. Because Party A is expensive, only Party A uses it less, so in the first month, two teams work together, and then all of them are completed by Party B, but equations need to be worked out.

The second question, let the vehicle speed x, the human speed y, 2(x+y)=6(x-y), and get x=2y, then the time is 2 (meeting time) *(x+y)/x=3 minutes.

Use equations

Set the vehicle speed v and the human speed v 1, and send a car in t minutes.

Then:

2(v+v 1)=vt

6(v-v 1)=vt

v=2v 1

2(2v 1+v 1)= 2v 1t

6v 1=2v 1t

t=3

A tram leaves the station every three minutes.