In a row at a bus stop, 'A' is 7th from the left and 'B' is 9th from the right. They both interchange their positions. Now A becomes 11th from the left. How many people are there in the row?

Draw a figure on the basis of above given question ,
D is between A and C. B is just right of C but left of F. E is not at the right end.
From figure , It shows that F is at the right end.
Sitting arrangement :-

Draw a figure on the basis of above given question ,
The student E sitting at the centre is facing only C and the student A is sitting facing the back of E. If D is sitting on the right of E.
Hence , it is clear that B is sitting on the left of E .
Sitting sequence :-

Draw a figure on the basis of above given question ,
C is between A and E. B is just to the right of E but left of D. F is not at the right end.
As shown in figure , B and E are sitting by the side of D.
Sitting sequence :-

Draw a figure on the basis of above given question ,
C is between A and E, B is just to the right of E but left of D , F is not at the right end.
As shown in figure , E is between B and C
Sitting sequence :-

According to question,
The Pigeon is to the right of the Parrot. The Sparrow is above the Parrot. The Crow is next to the Pigeon. The Crane is below the Crow.
It shows that Pigeon is at the centre .
Sitting arrangement :-

According to question,
We can draw a figure , It is given in the question that Sudha is not next to Tapti. This condition must be ommittted to solve the question. As shown in figure , Padma is in the middle.
Sitting arrangement :-

According to question,
We can draw a figure , in which Shekhar is to the immediate right of Dhanush. Bala is between Basha and Dhanush. David is at the extreme right end of the row.
As shown in figure , Dhanush is standing in the middle.
Sitting arrangement :-

Krishna is to the right of Samy.
There is no person between Samy and Krishna.
There is no person between Vaani and Sheela.
So, Saroj is sitting to the left of Samy.

According to question,
We can draw a figure , in which D is to the right of G. C is between A and B. E is between F and D. There are three persons between G and B .
As shown in figure , G is on the extreme left .
Standing arrangement :-

Draw a figure on the basis of above given question ,
A and B belong to Ruby House, while the rest belong to Emerald House. D and F are tall, while others are short. C and D are wearing glasses while others are not wearing.
D is from Emerald House. She is tall. She wears glasses.
sitting sequence :-