Solution:

4

Explanation:
5 = Five (four letters) => 4
7 = Seven (five letters) => 5
10 = Ten (three letters) => 3
3 = Three (five letters) => 5

Therefore, 9 = Nine (four letters) => 4.

Therefore the missing number is 4.

Solution:

125

Explanation:
The trick that has been used here is that all the corner digits have been reversed and then added. The sum is than placed in the center.

In the first square:
13 + 32 + 11 + 34 = 90

In the second square:
21 + 19 + 27 + 16 = 83

In the third square:
33 + 33 + 22 + 26 = 125

Thus the missing number is 125

Solution:

The solution is given in the attached image.

Solution:

The number 20 fits in place of question mark.

This is because (number in first column) / (number in second column) * 8 = number in third column.

Here (left number / middle number) * 8 = right number
E.g. (35 / 20) * 8 = (7/4) * 8 = 7 x 2 = 14
The same process can be used to find out the missing digit.

Solution:

There is no mention if you can use sign or not and thus the only possible way to get this is as follows:

(15 - 9) + (13 - 7) + (7 - 1) + (9 - 1) + (13 - 9)

If you solve inside the brackets, you will get the following equation
6 + 6 + 6 + 8 + 4
Adding all these numbers, you will get 30 which is the required sum.

Solution:

3

Explanation:
Number in the series = (Top Left Number * Bottom Left Number)/(Top Right Number * Bottom Right Number)
= (30 * 2) / (4*5)
= 3

Solution:

If you look closely, you will find a sequence in every alternating number.
192, 222 and 252 form one series where 30 is added each time.
021, 324 and 627 form one series where 303 is added each time.

Thus the next two numbers will be 282 and 930.

Solution:

60

Explanation:
1 + 5 = 12
But it can be true only if we multiply both digits with 2 and then add:
1*2 + 5*2 = 12

2 + 10 = 24
But it can be true only if we multiply both digits with 2 and then add:
2*2 + 10*2 = 24

3 + 15 = 36
But it can be true only if we multiply both digits with 2 and then add:
3*2 + 15*2 = 36

Similarly,
5 + 25 can be true only if we multiply both digits with 2 and then add:
=> 5*2 + 25*2 = 60

Therefore, the missing number is 60.

Solution:

Q

Explanation:
First Square:
6 + 4 + 4 = 14
N is the 14th letter.

Second Square:
4 + 1 + 7 = 12
L is the 12th letter.

Third Square:
5 + 6 + 10 = 21
U is the 21st letter.

Fourth Square:
14 + 2 + 1 = 17
Q is the 17th letter.

Solution:

100

Series of number that do not contain albhabet 'T'