Before the new road:

Section AP takes 20 minutes.
Section PB takes T/10 minutes, where T is the number of cars on the road.
Section AQ takes T/10 minutes.
Section QB takes 20 minutes.
So, the total time of travel from A to B before the new road is:
Total Time = 20 minutes (AP) + T/10 minutes (PB) + T/10 minutes (AQ) + 20 minutes (QB)

Now, with the new road that doesn't take any time, the total time of travel from A to B becomes:
Total Time = 20 minutes (AP) + 0 minutes (PQ) + 20 minutes (QB)

As you can see, the section PB and AQ times are no longer dependent on the number of cars (T/10), and they are replaced by the instantaneous PQ connection, which takes no time.

22 minutes ago, vacebi said:

the total time of travel from A to B before the new road is:
Total Time = 20 minutes (AP) + T/10 minutes (PB) + T/10 minutes (AQ) + 20 minutes (QB)

This is incorrect. Before the new road, any driver travels either by APB or by AQB, but not both. Their times do not add.

23 hours ago, Genady said:

This is incorrect. Before the new road, any driver travels either by APB or by AQB, but not both. Their times do not add.

Erm, this poster seems to be selling fake driving licence ID:

 

2 hours ago, exchemist said:

Erm, this poster seems to be selling fake driving licence ID:

 

Not surprisingly the form and the contents of their post above fit ChatGPT response well.