To get a straight line parallel to the y-axis you need to use the formula x= the number that x is equal to in the coordinate where it cuts the x-axis. Since you didn't specify the coordinate where your parallel cuts the x-axis I cant determine the actual number. Where your parallel cuts the x-axis you will get the coordinate (x,0). The number that is written instead of the x is the number you should use in the formula x=? instead of the '?'. I hope this wasn't too confusing.