Each team in the Atlantic, Southeast, and Central Divisions plays 4 games against the other 4 teams in its division, which equals 4 x 4 = 16 games within their own division.
Next, each team plays 6 of the teams from the other two divisions 4 times a year, which equals 6 x 4 = 24 games against teams from the other two divisions.
Each team then plays the remaining 4 teams from the other two divisions 3 times a year, which equals 4 x 3 = 12 games against those teams.
Each team also plays each team in the Western conference, which has 15 teams, twice a year for a total of 15 x 2 = 30 games against Western conference teams.
Adding up all these games, we have:
16 games within own division + 24 games against other two divisions + 12 games against remaining teams in other divisions + 30 games against Western conference teams = 16 + 24 + 12 + 30 = 82 games played by a team in the Eastern Conference during the regular season.