The link had several quilts in it (a round one, the cover, and a twirl), I do have a subscription to that magazine so I may be able to look up the actual pattern -- is it the twirling one?
Going to find the magazine. It looks to me like it is a block divided in to 5 sections on point with a pieced sashing. I don't think 12 inches is going to be easy, 12.5 probably would be -- is that close enough? But people can be clever in how they design their blocks and I might be missing something.
So... reductions in general. I use graph paper, I have for 30+ years. Say you have a life sized block graphed out with 4 squares to an inch, well, you can reduce it by redrawing it using 3 squares as your "inch". You can use 5 square to an inch architectural graph paper instead for a small reduction, still using 4 squares on the smaller grid.
But the easiest thing to do is to take what you want over to an office store like Staples with a self service copier, or maybe your printer has easy controls to enlarge/reduce especially if you have scanning abilities. Libraries often have copiers as well.
And remember, while math may not be your friend, he isn't going to come over and beat you up because you ignore him
