Do the Math: Secrets, Lies, and Algebra

In the eighth grade, 1 math whiz 1 popular boy, according to Tess's calculations. That is, until she has to factor in a few more variables, like: 3 cheaters (y), and 2 best friends (z) who can't keep a secret. Oh, and she can't forget the winter dance (d)! Then there's the suspicious guy Tess's parents know, but that's a whole different problem. Can Tess find the solutions?