Simplify the fraction to lowest terms 18/9

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.

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9

If a line is defined by the equation y = 5x + 2, what is the slope?