Screen Resolution: xrandr "cannot find mode"

Running the command

xrandr --addmode VGA1 1360x1020

would have done just as well.

xrandr (without arguments) will list the existing modes and the ones that can be added.

You seem to have typed a small "x" in the modeline (1360x1020), but a capital "X" in xrandr --addmode – Riccardo Murri