Question 762126
Plan1 (your plan): Total cost = 15 (monthly fee) + 0.05 * number of minutes
Plan2 (Friends plan): Total cost = 25(monthly fee) + 0.02 * number of minutes

Let us say both become equal after x number of minutes.

Since the total costs for both plans are equal for x minutes, we can equate the 2 expressions given above.

{{{15 + 0.05*x = 25 + 0.02*x}}}

{{{0.03*x = 10}}} or {{{x = 333.33}}}

Rounding off to the nearest minute, the two plans will cost the same after {{{highlight(333)}}} minutes.

:)