algebra
posted by Nic .
I need to write an equation for the following:
Denise's cell phone plan is $29.95 per month plus $.10 per minute for each minute over 300 minutes of call time. Denise's cell phone bill is $99.95. For how many minutes was she billed?

The fixed charge is 29.95 out of a 99.95 bill, so the minute charge is 99.9529.95 = $70
How many minutes can $70 buy at 10 minutes for a dollar? 
let x = over time (in minutes)
therefore,
29.95 + 10x = 99.95
10x = 99.95  29.95
10x = 70
x = 7 minutes
total minutes billed is 300 + 7 = 307 minutes
so there,, :) 
Um...
Each additional minute costs $0.10.
So $70 buys 70/0.10=700 minutes in addition to the 300 fixed minutes. The total is therefore...