Solution:

O

Explanation :
6 + 6 + 6 = N (last letter of sum i.e. eighteen)
7 + 7 + 7 = E (last letter of sum i.e twentyone)
8 + 8 + 8 = R(last letter of sum i.e twentyfour)
Therfore
0 + 0 + 0 = O (last letter of sum i.e. zero)

Solution:

See the picture for the answer. Don't worry if you have a different answer; this question can be solved with different numbers. However, do post your answer in the comments.

Solution:

118119

Explanation:
Number are generated as below
1 2
3 4
1 x 4 + 2 = 6 , 2 x 3 + 1 = 7 => 67

3 4
5 6
3 x 6 + 4 = 22, 4 x 5 + 3 = 23 = 2223

5 6
7 8
5 x 8 + 6 = 46, 6 x 7 + 5 = 47 = 4647

7 8
9 10
7 x 10 + 8 , 8 x 9 +7 = 7879

Based on above pattern, desired number will be calculated as :
9 10
11 12
9 x 12 + 10 = 118, 10 x 11 + 9 = 119 = 118119

Solution:

'T'

Explanation:
The letters around the center are actually depending on the letter in the center. They are advancing according to the numerical value of that letter.

For example, F, G, H and I are advancing by 1 because the center letter is A, which has the numerical value 1.

Again, G, K, S, and O are advancing by 4, because the center letter is D, which has a numerical value of 4.

Similarly, N has advanced by 6 from H, because the center letter is F, which has a numerical value of 6. Hence, the missing letter should be T.

Solution:

3! + 15 + 9 = 30

Explanation:
3! = 3 * 2 * 1 = 6
6 + 15 + 9 = 30

Solution:

73 & 48

Explanation:
We can get the number on the left by adding numbers above it and subtract the sum by 5. i.e.
8 + 11 - 5 = 14
14 + 10 - 5 = 19
19 + 16 - 5 = 30
30 + 21 - 5 = 46
46 + 32 - 5 = 73

Right column = left number above it + 2 => 46 + 2 => 48

Solution:

20

Explanation :
The sequence is given in the puzzle is :
11 15 19 12 16 ? 13 17 21 14 18 22

Let's break the given series as below:
11 15 19
12 16 ?
13 17 21
14 18 22

Now read the number from left hand side from top to bottom as :
So the number that will replace '?' is 20.

Solution:

9 - 8 + 76 - 5 + 4 + 3 + 21 = 100


Other ways of making number 100 (withiout using number 32)
98 + 7 + 6 - 5 - 4 - 3 + 2 - 1 = 100
98 - 7 - 6 - 5 - 4 + 3 + 21 = 100
9 - 8 + 76 - 5 + 4 + 3 + 21 = 100
98 - 7 + 6 + 5 + 4 - 3 - 2 - 1 = 100
98 + 7 - 6 + 5 - 4 + 3 - 2 - 1 = 100
98 + 7 - 6 + 5 - 4 - 3 + 2 + 1 = 100
98 - 7 + 6 + 5 - 4 + 3 - 2 + 1 = 100
98 - 7 + 6 - 5 + 4 + 3 + 2 - 1 = 100
98 + 7 - 6 - 5 + 4 + 3 - 2 + 1 = 100
98 - 7 - 6 + 5 + 4 + 3 + 2 + 1 = 100
9 + 8 + 76 + 5 + 4 - 3 + 2 - 1 = 100
9 + 8 + 76 + 5 - 4 + 3 + 2 + 1 = 100

Solution:

930

Explanation:
New number = Last number * multiplication factor (increased by 0.5 every time) + sum factor (increased by 5 every time)
10
10 * 0.5 + 5 => 10
10 * 1.0 + 10 => 20
20 * 1.5 + 15 => 45
45 * 2.0 + 20 => 110
110 * 2.5 + 25 => 300
300 * 3.0 + 30 => 930 , desired answer

Solution:

454585

Explanation:
Number is formed as (numA*numB)(numB*numC)(numC*numA)
Following the formular, 1st row will be like
5+3+2 => 5*3 3*2 2*5 => 151022
Simillarly
(9*5)(9*5)(9*5+9*5-5) => 454585