A cellphone company has a basic monthly plan of $30 plus 0.35 for any minutes used over 500 before receiving his statement John saw he was charged a total of $40.85 write and solve an equation to determine how many minutes he must have used during the month write an equation and solve?

The equation to this problem is:

$30 + $0.35. x = $40.85

where x is the amount of minutes that exceeds the 500-minute free limit.

$30 + $0.35. x = $40.85

$0.35. x = $40.85 - $30

x = $10.85 / $0.35

x = 31

The total amount of minutes used is 31 (charged) + 500 (free) = 531.

Response: 531 minutes.

:-)