you will need to make an equation for this. First, you know that he always pays $5 monthly, keep this in mind. Then it is given that his bill last month was 13.46 and that we need to know the minutes spent. for every minute, 9 cents or $0.09 is charged. In order to find out the time he spent, write the equation as such:
$5+$0.09(minutes)=$13.46 and solve from there
