Following the same logic, crack this mathematical puzzle ?

 

Two series alternate here, with every third number following a different pattern.
In the main series, 4 is added to each number to arrive the next.
In alternate series, 5 is subtracted from each number t arrive the next number.
Here in the main series 
3 + 4 = 7
7 + 4 = 11
11 + 4 = 15
15 + 4 = 19

In alternate series 
24 - 5 = 19
19 - 5 = 14...

The logic in the given puzzle is 

Addition of numeric values of corresponding letters in the first three figures gives respective corresponding letter in fourth figure. 

i.e, A = 1 , W = 23 , B = 2 => 2 + 1 + 23 =26 = 'Z'

Similarly, L = 12, K = 11 , A = 1 => 1 + 11 + 12 = 24 = 'X'

Here the missing letter is 'X'.

From first figure : each fig has the value of 20 => It has inside 4 figures => Each individual figure has the value of '5'

From second => Each Triangle has the value of '1' (bcoz it contains two in each)

From third => Figure star has the value of '4'

Then in fourth => 4 + 1 + 15 = 20

The puzzle's logic is

1st figure : (9-7) + (8-5) = 2 + 3 = 5

2nd figure : (15-6) + (11-2) = 9 + 9 = 18

similarly, 3rd figure : (9-6) + (17-5) = 3 + 12 = 15.

From all the hints given, 

only 042 satisfies and it unlocks the key.

In the first figure, number of triangles are 5.

In the second, the figure becomes double then the number of triangles also doubles.

i.e, 10. 

Starting from letter 'S' add 5 in the clock wise direction to get the next letter in English alphabets.

Here S + 5 => 19 + 5 = 24 => X

X + 5 = 24 + 5 = 3 => C

Similarly, 

B + 5 = G

Adding the corresponding numbers in first and last figures gives the corresponding number in the middle figure.

i.e, 4 + 3 = 7

13 + 2 = 15

2 + 4 = 6

9 + 1 = 10