acer chromebook r11 screen brightness

#acer chromebook r11 screen brightness
sudo mkdir /etc/X11/xorg.conf.d
sudo vim /etc/X11/xorg.conf.d/20-video.conf

Section "Device"
    Identifier  "Intel Graphics"
    Driver      "intel"
    Option      "Backlight"  "intel_backlight"
EndSection

cat /sys/class/backlight/intel_backlight/max_brightness
cat /sys/class/backlight/intel_backlight/brightness
echo "921" |sudo tee /sys/class/backlight/intel_backlight/brightness

xbacklight -dec 5
xbacklight -inc 5
xbacklight -set 70