It is given that the first plan has no monthly fee but charges $0.20 for each
minute of calls.
The second plan has a $24 monthly fee and charges an additional $0.15 for each minute of calls.
We have to determine the number of minutes of calls for which the costs of
the two plans be equal.
[tex]0.20x=24+0.15x[/tex][tex]0.20x-0.15x=24[/tex][tex]0.05x=24[/tex][tex]x=480\min [/tex]Hence the number of minutes of calls required is 480 min.