Exhibit the complete table of multiplication for (mathbb{Z} / 15 * mathbb{Z})∗, and use this to give a solution to the equation 7X ≡ 3 (mod 15).

Exhibit the complete table of multiplication for (mathbb{Z} / 15 * mathbb{Z})∗, and use this to give a solution to the equation 7X ≡ 3 (mod 15).

I have no idea how to start this question? How do you build a multiplication table for (Z/15Z)*?