Can you help me with these four problems, please.

How to find the exponential function y=ca^x, with points (1,2) and (2,1)

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.

See attachment below and find the equivalent of tan(∠qsr)