You look at your friend, the streetlight only just allows you to see his green eyes. "No, you know that I'm underage, and you are too." He looks confused by your statement, but the corners of his mouth turn upwards and his eyes narrow. "That's the point." He says smugly as he steers into your eyes. "Don't drink that. Don't you know what it does to your body? Plus, if you do, I'll tell an adult." You tell your friends to get up, which they do, and you all briskly exit the park, none of you look behind you, you've got to get out of there.
The interpersonal factor that would have influenced this decision is your responsibility with telling an adult about the situation even if it would be against your friend. Often teenagers do not tell others about their friend's drinking because they would prefer to not go against their friend. By telling an adult, you are helping a friend to stop drinking.
The societal factor that would've influenced your decision is the fact that you are aware that both you and your friends are underage, and that drinking underage is illegal. You also know what alcohol does to you body and the consequences of drinking alcohol. Being made aware of the consequences of alcohol has helped prevent you and others from drinking, and has helped you make the best decision. These facts may have been learned at school or from parents, but you know how wrong it is.
The personal factor that would have influenced this decision is how much you value your friendships. You prioritize you and your friend's health and safety over looking cool. Being able to say no and remove yourself from situations is a valuable skill to have. This is the best decision to have made because none of your friends got hurt and that an adult was informed about the situation.
The interpersonal effect of this decision is that you most likely lost a friend in the process. A friend that you trusted offering you alcohol when they know that you are both underage will definitely damage that friendship and a lot of trust will be lost between the two of you. Although, other people involved in the situation will know how to turn down alcohol to a friend. Multiple people learned from this decision and this is one thing that makes this the best outcome.
News like this would spread fast, to other teenagers and adults, other people would make decisions about the best way for them to act in this situation. Parents and teachers will have talks about alcohol with their children. The societal effect of this decision is that multiple people would become aware of underage drinking which makes this the best decision.
The personal effect of this decision is that a lot of confidence would have been obtained. By refusing an offer from your friend for something that is wrong and harmful can make one so much more confident and aware. If a situation like this ever occurs again you have the skills to confidently decline the offer.