Given this setup, how far does the book slide? This is a fairly basic kinematics problem once you have acceleration, which you can get with application of Newton's 1st and 2nd laws. Which is what I endeavored to do but I keep getting the wrong answer for acceleration.
I suspect I'm missing something with my free body diagram, but I've gone over it several times and I don't know what I could be missing.
You have the angle wrong. The angle between $W_b$ and the plane is $90^\circ-20^\circ=70^\circ$