I'm not good at this stuff, and this is old. However..
You have 165" on the wall
Each frame is 28"
That leaves 53" of free space on the wall
If you started the end posters against the wall it would leave 17.66666 in between the 4
If you spaced them evenly you would leave 10.6" from the first wall to the next poster, and so on, until you hit the next wall.
Assuming I haven't screwed this up already - The first nail would go in at 24.6" - the next at 63.2" - 101.8" - 140.4"
Like I said.. not good at this stuff.. but it took me all of 5 minutes to mill this out.