Acoordinate plane with number of text messages on the x-axis and number of minutes used on the y-axis, with points plotted at, (10, 20), (20, 40), (30, 60), and (40, 80). a prepaid cell phone charges a preset number of minutes to use text messaging. the graph represents y, the number of minutes used for x, the number of text messages sent and received. is there a direct variation? which equation represents the relationship? yes, y = 2x. yes, y = 20x. no, y = x + 10. no, y = x + 20.