Solution:

Wednesday

Explanation :
There is two way to interpret this.
A) If x + 1 ==> x - 1
Then
x ==> x - 2
x - 2 = Friday
x = Sunday

B)If x - 1 ==> x + 1
Then
x ==> x + 2
x + 2 = Friday
x = Wednesday

Option B) makes sense and hence the answer.

Solution:

Federer serves first

Explanation:
The one who serves first can serve 5 and other will serve four.

== Option A ==
If Federer serve 4 and Nadal serve 5
Then five service breaks and Federer winning 6:3 not possible.

== Option B ==
Federer serve 5 and Nadal serve 4
There are five service breaks and score is Federer 6 - Nadal 3
i.e
On Federer serve, Federer wins 3 and lost 2
On Nadal serve, Federer wins 3 and lost 1

Solution:

It can be solved as shown.

Solution:

Rashid's son-1: 1 11 21 31 41 51 61 71 81
Rashid's son-2: 2 12 22 32 42 52 62 72 73
Rashid's son-3: 3 13 23 33 43 53 63 64 74
Rashid's son-4: 4 14 24 34 44 54 55 65 75
Rashid's son-5: 5 15 25 35 45 46 56 66 76
Rashid's son-6: 6 16 26 36 37 47 57 67 77
Rashid's son-7: 7 17 27 28 38 48 58 58 78
Rashid's son-8: 8 18 19 29 39 49 59 69 79
Rashid's son-9: 9 10 20 30 40 50 60 70 80

Solution:

The code is 645
Explanation :
A) From Clues 1st and 2nd we know that one 9 is not in the code
B) From Clue 2nd we know that 9 3 and 8 are part of code
C) From Clue 3rd we know that 4 and 6 are part of code
D) From Clue 5th we know that 1 and 2 are not part of the code as we know 6 is part of the code and just 1 of 3 numbers is part of code.
E) From Clue 4th we know that 5 is also in the code as 8 and 1 are not part of code.

So the code is: 645

Solution:

They are all anagrams of time-related words.

1. CHARM: MARCH
2. DYNAMO: MONDAY
3. YAM: MAY
4. REAY: YEAR
5. EAR: ERA
6. ONE: EON
7. TOADY: TODAY

Solution:

73

Explanation:
It's a very famous puzzle known as "Josephus Problem Puzzle". It can be solved in various ways but the trick to solve this problem is illustrated below.

Binay number of 100 is: 1100100
complement pf 100 is 0011011, whose decimal equivalent is 27.
The desired answer will be 100 - 27 = 73

Solution:

Step1 : Mr.Hinx and Supermodel1, Mr.Hinx back
Step2 : Mr.Hinx and Supermodel2, Mr.Hinx back
Step3 : Blofeld and JamesBond, Blofeld back
Step4 : Mr.Hinx and Secret Diary, Mr.Hinx back
Step5 : Mr.Hinx and Blofeld, Mr.Hinx back
Step6 : Mr.Hinx and secretary1, Mr.Hinx back
Step7 : Mr.Hinx and secretary2

Solution:

The chocolates in the boxes will be as follows:
Box 1 = 1
Box 2 = 2
Box 3 = 4
Box 4 = 8
Box 5 = 16
Box 6 = 32
Box 7 = 64
Box 8 = 128
Box 9 = 256

Here we have taken a geometric progression to facilitate any number of chocolates demanded. In the last box, we will place the number of chocolates left:

Box 10 = 489

If you try now, you will be able to do what is asked.

Solution:

First stack of cards = 11
Second stack of cards = 7
Third stack of cards = 6

First move:
First stack of cards = 11 - 7 = 4
Second stack of cards = 7 + 7 = 14
Third stack of cards = 6

Second move:
First stack of cards = 4
Second stack of cards = 14 - 6 = 8
Third stack of cards = 6 + 6 = 12

Third Move:
First stack of cards = 4 + 4 = 8
Second stack of cards = 8
Third stack of cards = 12 - 4 = 8