Find the mean of 17 10 9 8 8 12 6

Can someone me out here and the tell me the greatest common factor

For what value of (y) is 3^3/3^y =1/9

Dean and karlene get paid to write songs. dean is paid a one-time fee of $20 plus $80 per day. karlene is paid a one-time fee of $25 plus $100 per day. write an expression to represent how much a producer will pay to hire both to work the same number of days on a song.