Look at the 2nd column and see where a 7 CAN'T go. From there you can deduce that, in the top-left sector a 7 HAS to go in either the center or bottom center. From there you can deduce that a 7 can't go in the top-left square, therefore a 6 must go there. Hope this helps.
In the top-centre section an 8 can only exist in the bottom-centre or the bottom right square. In the middle section an 8 can only exist in either the top centre square or the top-right square. Because an 8 has to go in either the centre or right side of these two sections, an 8 has to go in the left side for the bottom-centre section. Therefore a 4 must go into the bottom-right square of the bottom centre section.
Currently trying to solve the hardest puzzle in my sudoku book.
There's a 1 in the TL sector, a 3/8 ghost pair in the C sector, a 5/8 ghost pair on the 9th row, and a 6 in the BC sector, BC cell. That's all I can find. If we can solve this puzzle there would be no more need to play sudoku ever again.
EDIT: 2/9 ghost pair in the 5th column
Last Edit: Sept 19, 2013 23:58:24 GMT -5 by Deleted
I solved a few 6s. I noticed that a 3 didn't belong in the 1st row in the TC & TR sections and had to be in the TL setion on the top row. An 8 couldn't exist on the CR and BR squares of the TL section, and a 4 couldn't exist in the right-side squares. This means 3,4,8 must exist in the top 3 squares of the TL section, leaving 79 for the last two squares. Looking in the 4th column the only places a 2 or a 6 could go was in the 3rd or 5th row. Also, with the new 6 in the CL section and that 7/9 ghost pair, this means a 2 must go into the CR square of the CL section.
Kenken/Calcoduko in a nutshell: 4x4 - You have a severe case of dyscalculia if you can't solve this. 6x6 - Ideal for newcomers who want a bar test or play the game casually 8x8 - You will meet a competent puzzle worth your skills. If you're really good you'll feel like you're skipping parts of the puzzle that you feel as though weren't supposed to solve until later 9x9 - This will take a while- you better have your s*** together or this puzzle will cream your ass. 10x10 or 12x12 - I just gave up on a 12x12 kenken puzzle because I made an error and didn't realize it until ~50 steps later- literally ~50 steps later. 15+x15+ You are bats*** insane.