Or more compactly,
echo 15 | sudo tee -a /proc/acpi/video/VGA/LCDD/brightness echo 5 | sudo tee -a /proc/acpi/video/VGA/LCDD/brightness
Or more compactly,
echo 15 | sudo tee -a /proc/acpi/ video/VGA/ LCDD/brightness video/VGA/ LCDD/brightness
echo 5 | sudo tee -a /proc/acpi/