For this case we have as a fact that Tony pays monthly $ 27 for telephone service, in addition to $ 0.04 per minute of additional use.
If "M" represents the number of minutes used by Tony in a month we have:
[tex]27 + 0.04M[/tex]
If the minimum that has been charged in a month is $ 70.44 then:
[tex]27 + 0.04M \geq 70.44[/tex]
Clearing "M" we have:
We subtract 27 on both sides of the inequality:
[tex]27-27 + 0.04M \geq 70.44-27\\0.04M \geq 43.44[/tex]
We divide by 0.04 on both sides of the inequality:
[tex]\frac {0.04M} {0.04} \geq \frac {43.44} {0.04}\\M \geq 1086\ minutes[/tex]
Tony uses at least 1086 minutes per month.
Answer:
Tony uses at least 1086 minutes per month.
