What is the domain of the function f(x)=45/(x-23)?

How to do this , and can some one explain

60 musicians applied for a job at a music school. 14 of the musicians play both guitar and drums. what is the probability that the applicant who gets the job plays drums or guitar?

The graph of f(x) is obtained by reflecting the graph of f(x)=-3|x| over the x-axis. which equation describes f(x)? a) f(x)=3|x| b) f(x)=|x+3| c) f(x)=-3|x| d) f(x) = - |x+3|