geometry
posted by abigail .
a phone company charges a flat monthly fee of $15 for cell phone services, plus an additional fee for every minute you talk. in a given month, you are charged $36 for the 24 minutes you talked( not including the $15 flat fee.) let the total cost be c(in $) and the time you talk be t(in minutes)
how do i find the dependent and independent variables, and the "fixed" cost of the phone plan, and what cost do you pay per minute. and how do i write an equation relating c and t

how is this geometry?
The independent variable is the one that can change by itself. In this case, the number of minutes you talk: t.
c = fixed bill + minute rate*t
The charge for each minute = $36/24 = 1.50 (pretty pricey!)
c = 15.00 + 1.50t 
how would you write an equation for a phone that cost $30 plus 30 cents per minute

how would you write an equation for a phone that cost $30 plus 30 cents per minute