Hey I am going to play the upright bass for a jazz choir group at my high school and there is white powdery stuff on the strings. I asked some people and they think it is stuff from the bow. If this is true, is there a simple solution of getting it off besides playing it for a week or buying new strings? Thanks.

Oh yeah I am also not using the bow. I am using my fingers.

The "powdery stuff" would be rosin. I once used (a small amount of) rubbing alcohol on a cloth to remove really caked-on rosin from cello strings. If it's not really caked-on, it's not doing any harm: Don't worry about it--or brush it off if you like.