Question 31906
Hello!
Let's call X to the number of minutes of long-distance calls you plan to make.

The cost of plan A is given by {{{25+0.05X}}}

The cost of plan B is given by {{{5+0.12X}}}

Plan B is advantageous when its cost is lower than plan A's. Therefore, we set the inequality

{{{5+0.12X < 25+0.05X}}}

And then solve for X. This will give us the range of minutes for which B is more convenient.

Subtract 5 from both sides of the inequality to get:
{{{0.12X < 20+0.05X}}}
Now subtract 0.05X:
{{{0.12X - 0.05X < 20}}}
{{{0.07X<20}}}
Finally, divide by 0.07 to get:

{{{X < 20/0.07}}}
{{{X  < 285.71}}}

So plan B is advantageous if you plan to use less than 286 minutes of long distance calls.


I hope this helps!
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