Seven boys Ajay, Mihir, Rohit, Karan, Vaibhav, Nitin and Sanjay are sitting on a straight bench facing towards the north. Karan is sitting at the extreme left end and second to the left of Rohit. Mihir is the immediate neighbour of Rohit and Vaibhav. Nitin is sitting to the immediate left of Sanjay.
Who is sitting second to the left of Mihir?

Let's place the 7 positions from left to right: 1, 2, 3, 4, 5, 6, 7.
"Karan is sitting at the extreme left end" → Position 1 = Karan.

"Karan is second to the left of Rohit" → Position 3 = Rohit (since Position 1 is second to the left of Position 3).

"Mihir is the immediate neighbour of Rohit and Vaibhav" → Mihir must be adjacent to both Rohit and Vaibhav. Since Position 3 is Rohit, Mihir and Vaibhav must be at Positions 4 and 5 respectively to stay together with Rohit. Thus, Position 4 = Mihir, Position 5 = Vaibhav.

"Nitin is sitting to the immediate left of Sanjay" → This requires two consecutive vacant spots. The remaining positions are 2, 6, and 7. The only consecutive spots left are 6 and 7. Therefore, Position 6 = Nitin, Position 7 = Sanjay.

The remaining vacant spot (Position 2) goes to Ajay.

The final linear arrangement from left to right is:

Karan→Ajay→Rohit→Mihir→Vaibhav→Nitin→Sanjay
We need to find who is sitting second to the left of Mihir (Position 4):

Immediate left of Mihir is Rohit (Position 3).

Second to the left of Mihir is Ajay (Position 2).