There is a certain logic determining the numbers in the grid below.

What is the answer to the question mark in Grid "D"?
......A......
.9........5
15......27
......B...
0...........1
3...........0
.....C....
.6.........12
36........18
......D......
15.........2
.6..........?

? = 45. The rule is that the bottom left corner is the upper right times 3, while the bottom right is the upper left times 3.

1st number of bottom line is 3times of upper line right number and
2nd number of bottom line is 3times of upper line left number
so the required number at blank is 45