I really don't understand this problem:

Two planets X and Y travel counterclockwise in circular orbits about a star. The radii of their orbits is in the ratio 3:2. At some time, they are aligned, making a straight line with the star. Five years later, planet X has rotated through 89.0 degrees, how many revolutions has Y turned at this time?

What you need to know here are Kepler's laws of planetary motion:

http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion

That's way more information than you'll need, but concentrate on Kepler's third law. Simply put,

T1^2/T2^2 = r1^3/r2^3

Where T is the period required to orbit the sun, and r is the radius from the sun.

Hope that helps you out.