I am having trouble starting out these classes, and i'm not understanding how to find a class. Any ideas on where to start would be great.

Consider the relation I on real numbers defined by xIy <=> x-y is an integer. Describe the equivalence classes of 1/2, 2, pie and 3/2

where <=> means if and only if.

What I'm doing is as follows:

[1/2]={xE real numbers : xR0} then i don't know what to do?