Solution:

3

Explanation:
Fernando + Alonso + McLaren = 6
Fernando x Alonso = 2
Alonso x McLaren = 6

Given.
Fernando x Alonso = 2
Alonso x McLaren = 6

Rewriting Both equations in terms of Alonso,
Fernando = 2/Alonso
McLaren = 6/Alonso

Replacing above values in equation "Fernando + Alonso + McLaren = 6"
2/Alonso + Alonso + 6/Alonso =6
(2 + Alonso^2 + 6)/Alonso = 6
8 + Alonso^2 = 6Alonso
Alonso^2 - 6Alonso + 8 = 0
(Alonso - 4) (Alonso - 2) = 0

Therefore;
Alonso = 4 or 2

Let's take value of Alonso as 2
Fernando = 2/2 = 1
McLaren = 6/2 = 3

Therefore;
McLaren x Fernando = 3 x 1 = 3

Solution:

7, 4, 6, 5, 8

Solution:

1/2

one of two is the possibility
1. If any of the first 99 people sit in Abhishek seat, Abhishek will not get to sit in his own seat.
2. If any of the first 99 people sit in Aishwarya's seat, Abhishek will get to sit in his seat.

Solution:

The wise man told them to switch the horses and then race. In this manner, both of them will be willing to race as fast as they can to prove that the other horse (his own horse) is slow.

Solution:

Playing chess

Game needs two players so Brother-8 is playing chess with Brother-2

Solution:

See the figure for the answer. Wasn't it a bit tricky?

Solution:

Read the question carefully again. New Year do falls after Christmas but that happens if two different years. The question is put up against the year 2050 and thus there will be 51 weeks and 2 days in between them as New Year will appear on 1 January 2050 and Christmas will happen on 25 December 2050.

Solution:

10

Explanation:
Equation 1 + 9 + 11 = 1 can be derived from
One (o) + nine (n) + eleven (e) = one => 1

Similarly for equation,
12 + 11 + 9
Twelve (t) + eleven (e) + nine (n) => ten (10)

Solution:

When you were inside the shed, the murderer replaced the lock with his own one that was identical to your original lock. When you locked the store room, you did not require a key and there was nothing abnormal for you. When you left, the murderer opened the lock with his key, planted the dead body inside and replaced the lock again putting the original lock in the place. He then closed it without any problem.

Solution:

It can be done as shown in the picture below.

Solution:

888 + 88 + 8 + 8 + 8 = 1000