Hint
Look at the letter positions in the alphabet.
Answer
R.
If you take the alphabetic positions of each letter in a row, the total is always 56.
Double-Checking
Y + G + W + A = 25 + 7 + 23 + 1 = 56
K + L + R + O = 11 + 12 + 18 + 15 = 56
Z + J + P + D = 26 + 10 + 16 + 4 = 56
V + F + T + H = 22 + 6 + 20 + 8 = 56
?
Puzzle 155
This BrainBashers safe has a rather unusual control panel.
In order to open the safe, you have to press every single square once only, in the correct sequence, ending on the square marked E.
Each square indicates which square to press next, for example, 2U means move up 2 squares and 3R means move right 3 squares.
Can you determine which square you must start with?
3R
4R
2R
2D
2R
4D
2D
2R
1U
1U
3D
2D
1R
2L
3D
1D
3R
1R
2L
4L
1D
1U
4R
2L
3D
2D
2L
4L
4U
1L
2D
E
2R
1D
4L
1R
1D
1R
4U
2R
3L
1D
5U
5U
2L
2R
2U
5U
2L
Note: this puzzle is not interactive, and the safe buttons cannot be clicked.
Reasoning
Take the third letter of the first word
+ the second letter of the second word
+ plus the first letter of the first word
+ plus the fourth letter of the second word.