Solution:

180

2 + 2 = 4 {2 * 2 * 1}
3 + 3 = 18 {3 * 3 * 2}
4 + 4 = 48 {4 * 4 * 3}
6 + 6 = 180 {6 * 6 * 5}

Solution:

17/19

series is 2/1 3/4 5/7 7/10 11/13 13/16
Numerator is prime number series 2-3-5-7-11-13-17
and Denominator is +3 series 1-4-7-10-13-16-19

Solution:

Stephen is your grandson.

Let us explain how:
Your Uncle's sister can be your mother or can be your aunt. But in the question, you have mentioned that we have to look for the closet relation thus, it will definitely be your mother.
Now, your mother's granddaughter can either be your daughter or your niece. Again, daughter is the closer relation.
Advancing forward, your daughter's son is without a doubt your grandson.

Solution:

0 or 16

Explanation:
If you notice, then there is no pattern in this image between the numbers. The only thing is that the numbers are all jumbled up and continuous.

Therefore, the missing number can either be 0 or 16.

Solution:

88

Explanation:
14 -20 34 -54 ? -144
The number is difference between right number and left number.
i.e

example
14-(-20) = 34
-20-(34) = -54
34-(-54) = 88 answer
-54-(88) = -143

Solution:

9

cube of prime numbers
2*2*2 => 8
3*3*3 => 27 ...Answer
5*5*5 => 125
7*7*7 => 343
11*11*11 =>1331

Solution:

4

92 - 38 = 54
5 is given and 4 is missing

Solution:

4

6*3 equals 18
7*9 equals 63
6*4 equals 24
7*6 equals 42, ? should be replaced by 4.

Solution:

The answer is 1

6 {6^1}
25 {5^2}
64 {4^3}
81 {3^4}
32 {2^5}
1 {1^6}

Solution:

1806

each number is multiplied by the number+1
1x2 = 2
2x3 = 6
6x7 = 42
42x43 = 1806
1806x1807 = 3263442