You should already know that the Eagles are the favorite to win and that you should expect less than even money on a correct pick here. You should also know that the Falcons are the favorite, and you should expect better than even money on a correct pick here. Having this in mind every time before you start your calculations will protect you from making a mistake and calculating the completely wrong direction.
In addition to the spread bet, a very common "side bet" on an event is the total (commonly called the over/under or O/U) bet. This is a bet on the total number of points scored by both teams. Suppose team A is playing team B and the total is set at 44.5 points. If the final score is team A 24, team B 17, the total is 41 and bettors who took the under will win. If the final score is team A 30, team B 31, the total is 61 and bettors who took the over will win. The total is popular because it allows gamblers to bet on their overall perception of the game (e.g., a high-scoring offensive show or a defensive battle) without needing to pick the actual winner.
Armed with the knowledge of how to remove vig, it's now possible to prevent yourself from making the same mistakes that the majority of bettors make. Most bettors understand the importance of line shopping (i.e. comparing the lines and odds at different bookmakers and betting sites). However, if they fail to also understand how moneylines and vig work, then they're probably going to make wagers where they think there's positive expected value (+EV), even though there's not.
Sports betting has been around since 1000 B.C in China, where betting on animal fights was commonplace. In ancient Rome, one could wager on the Gladiatorial games. The idea of betting on sports is as old as organized sport itself. But up until the 1940s, bettors were fairly limited in what kind of bets they could make. The standard system of odds would allow bets on, for example, the 3-1 odds that the Steelers would beat the Browns.