Solution:
Let x represent a number of calling minutes. According to the problem, we want:
[tex]11\text{ + 0.11 x = }27\text{ + 0.07 x}[/tex]now, putting the similar terms together, we obtain:
[tex]0.11\text{ x - 0.07 x = 27 -11 }[/tex]this is equivalent to:
[tex]0.04x\text{ = 16}[/tex]now, solving for x, we get:
[tex]x\text{ = }\frac{16}{0.04}\text{ = 400}[/tex]then, the correct answer for the first question is:
400 minutes is the number of minutes the two plans cost the same
now, for the second question, we can replace the above value (400 minutes) into the following equation:
[tex]11\text{ + 0.11(400) = }55[/tex]so that, the correct answer for the second question is:
$55 is the cost when the two plans cost the same