Do the Math #2: The Writing on the Wall by Wendy Lichtman

Eighth grade, like algebra, has become pretty complicated for Tess. For one thing, there are the patterns she's noticing everywhere—like how charming-on-the-outside Richard keeps playing scary pranks on her, and how annoying copycat Lynn always has to follow what everyone else is doing. Then there's the pattern of graffiti that keeps appearing on the wall by her school—could those numbers be a code meant for Tess? Is it up to her to find out what they mean? And most importantly, if Damien keeps up with his pattern of waiting for her after school, does it mean he likes her? Or is that just a coincidental system?

Tess looks for formulas to help her figure it all out, but she's afraid there may be none. Sometimes you have to make up your own solutions.

Sometimes, you just have to risk it.