I used a black cardstock base to mimic a chalkboard feel and a white colored pencil to write the equation. I was definitely having some algebra class flashbacks when I was copying down the equation and trying to make sure I got it right.
Isn't this geeky little bear so cute? He's called "Teacher," but I used him as an engineer. Because the bear, which I cut at 3 inches, is holding a black laptop, I stuck a piece of argyle purple paper behind him. The paper is from Paper Studio's Basics pad (I can't remember if it's the 12x12 or the 8x8, because it was just a leftover scrap I pulled out). I kept a little bit of the black paper still visible around the edges.