Question

a cell phone company charges 30 dollars per month with a 15 dollar activation fee plus 0.07 per minute if mr Perez's February bill was 74.40 dollars how many minutes did he talk

Answer 1

Let x be the minutes spent on call on the cell phone.

The expression for the monthly fee would be:

`0.07x+(30+15)`

This way, if the monthly fee was $74.40, that means

`74.40=0.07x+45`

Solving for x ,

`\begin{gathered} 74.40=0.07x+45 \\ \rightarrow74.40-45=0.07x \\ \rightarrow(29.4)/(0.07)=x \\ \Rightarrow x=420 \end{gathered}`

We get that Mr. Perez used his cell phone for 420 minutes