Answer:
[tex]89\ \text{minutes}[/tex]
Step-by-step explanation:
Let the number of minutes Ravi spoke for be [tex]x[/tex]
The fixed monthly fee is $2
Per minute Ravi is charged 12¢ = $0.12
The charge in a month will be
[tex]y=2+0.12x[/tex]
In one month Ravi was billed $12.68. So [tex]y=12.68[/tex]
[tex]12.68=2+0.12x\\\Rightarrow x=\dfrac{12.68-2}{0.12}\\\Rightarrow x=89\ \text{minutes}[/tex]
So, Ravi spoke for [tex]89\ \text{minutes}[/tex] that month.
