Haha. Well you can only have one of each number from 1-9 in each row/column/box right? So you follow the 1s over, and the cell it doesn't intersect with, where the X is, means the 1 goes there... I can't really find an easy explanation for you unfortunately. I learned by just playing. Can anyone help me out here?
Hey, I think I'm getting the hang of it. Took me 20 minutes to do the first one on easy though. But only 11 for the second, and 12 for the third! I'm getting better, slowly.