How do you win a game where everybody else loses lane and you go even?

try to make plays to get ahead. be agressive.

if it fails, you losing game is shortened if it works, great, maybe you can carry

All you can do is try. It's a team game, so if the majority of your team loses, you're supposed to lose. Unfortunately it is what it is.

if you have a superior team fight comp, catch enemies off gaurd, capture objectives, win team fights. maybe you have a good split push comp, just defend and split push.

their are options but it all boils down to one thing. your team needs organization/communication and work together better than the other team does.

If your lane went even and every other lane (including jungle) lost, then the odds are you're going to lose that game. You have to accept that reality FIRST and then plan accordingly.

During the mid game, your team is going to have to play defensively. You will need to ward like crazy, don't overextend, and wait for your opponents to make mistakes. Go for picks, not straight up fights. If you have a split pusher, have them ward themselves up, draw attention, and then try to regroup and force fights when the enemy has reduced numbers.

Stay positive and don't flame is #1 rule. Try to be friendly and rally their support into generally intelligent tactics. Other than that I have no 'gameplay' advice.

As it depends on who you play, tailored advice is not possible from me. I main Shyvana. I rally my team to distract while I split push, or to create pressure while I sneak objectives.

another good tactic is to stall the game:

If your opponents are lv.18 with full build, it doesn't matter if they are 27/1/16, they can't get any stronger. Meanwhile your team is still leveling up and getting items, effectively closing the power difference.

http://i.imgur.com/PUDcImR.png?

some games u just dont win, you arent meant to win that game, but split pushing would be the best option, but a decent team will just 5man vs it.

you have to constantly make plays, steal baron/drag etc to get back in it, i had a game 2-3 days ago in ranked on veigar, i stole 3 dragons in a row over the wall with wq combo, because in this elo people dont do stuff like learn from mistakes, or ward behind the pitt to prevent this.

You probably don't unless your teammates make a recovery.