Hello!
Since Trey pays a flat monthly $6 fee, we can subtract that from the total bill:
$12.27 - $6 = $6.72
That leaves us with a total of $6.72 paid for minutes. We are told that Trey is charged 8 cents per minute of usage. Using the information above, we can create the following equation:
$0.08 x (minutes) = $6.72
Now divide $0.08 from both sides of the equation and simplify:
[tex]\frac{0.08}{0.08}[/tex] x (minutes) = [tex]\frac{6.72}{0.08}[/tex]
minutes = 84
We have now proven that Trey was billed for 84 minutes.
I hope this helps!
