Question 96528
Suppose the time for which a person talks be x minutes.
Assume: x > 1


So, the cost is $ 0.36 + $ 0.21(x - 1) = $ (0.21x + 0.15).
This value has to be less than or equal to $ 3.


Hence, {{{0.21x + 0.15 <= 3}}}
{{{0.21x <= 3 - 0.15}}}
{{{0.21x <= 2.85}}}
{{{x <= 2.85/0.21}}}
{{{x <= 13.57}}}


As x has to be a positive integer so x = 13.