Tim's phone service charges $27.22 plus an additional $0.15 for each text message sent per month. If Tim's phone bill was $30.97, which equation could be used to find how many text messages, x, Tim sent last month? A. $0.15x + $27.22 = $30.97 B. $27.22x - $0.15 = $30.97 C. $27.22x + $0.15 = $30.97