For 2 I am not sure what (mod 3) means and how to solve. For 3 I don't understand what to do with the different variables.

2 . Let A = 1 - 9, - 7, - 5, - 2, 0. 1. 1, 6. 8) , and consider the equivalence rela` tion R on A defined by IRU IN IE Y ( mod 3 ) . Determine A / RX. 3 . Let A = R, and consider the equivalence relation R on A defined by I Ry' iff LI ] = Ly ] , where [ I ] represents the greatest integer less than or equal to 2 . Determine* the following* ( Note carefully* that [I ] represents the equivalence class of I , not the greatest integer function which is denoted above by [ I ] . )