I'm not very Clever

[Darrin Turnbull]

42 , i read it in a guide somewhere

[Daniël Bos]

I'm not clever.

 

Got that straight away though, a touch of autism sure is helpful sometimes...

[spudulike]

Pretty simple although there is no definite way of making sure both diagonals should add up to 40 but seems like the obvious answer! These question setters just like messing with the question to make it seem more difficult than it really is!

[Billhook]

But who states that you have to take a diagonal line? No one

 

I add the "C" shape of G 11 to B 6 to P 20 to make 37

 

I take the mirror image and add S 23 to B 6 to make 29

 

The missing number must therefore be 37 minus 29 = 8 or the letter D

[Billhook]

42 , i read it in a guide somewhere

 

Nah, that was the answer to "what is six times nine!"