Solution:

569

Explanation:
Number in the triangle in ant-clockwise are: 15 12 and 18
The Central number is formed by there largest factor i.e
15=> 3 * 5 => largest factor is 5
12=> 2 * 6 => largest factor is 6
18=> 2 * 9 => largest factor is 9.

Therefore required number is 569.

Solution:

24

Explanation:
21 * 4 - (4 * 4) = 68
12 * 4 - (4 * 4) = 32
17 * 4 - (4 * 4) = 52
10 * 4 - (4 * 4) = 24

Solution:

40

Explanation:
A) 123 + 0 = 16
20 - (1+3)

B) 234 + 0 = 24
30 - (2+4)

C) 345 + 0 = 32
40 - (3+5)

Then
456 + 0 = 40
50 - (4+6)

Solution:

yaM

Explanation:
voN luJ ? raM beF

Step-1: Reversing the input text gives us:
Feb Mar ? Jul Nov

Step-2: Replace by month numbers
2 3 ? 7 11

Step-3: Find the relation
They all are prime numbers, the missing number here is "5".

Step-4:
5th month is May and reverse of May is yaM (answer)

Solution:

A

Explanation:
Pi = 3.141592653.....
All images are related by pi value i.e "The number of straight lines on each shape corresponds to the digits of pi."

Solution:

21982030

Explanation:
Next number formed is (number * (number-2)) - number;
i.e
(5 * 3) - 5 => 10
(10 * 8) - 10 => 70
(70 * 68) - 70 => 4690
(4690 * 4688) - 4690 => 21982030

Solution:

2003.

Explanation:
Its a series of prime numbes.

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