If you want a movie to show on a Galaxy Tablet 3, what is the significance of that 1280 x 800 pixels. Do you mean 1280 x 720 which would be 720p?
1. What version of Premiere Elements are you using and on what computer operating system is it running? Do you have a NTSC or PAL set up?
For now, I will assume Premiere Elements 12 on Windows 7, 8, or 8.1 64 bit and a PAL set up.
2. Look at
with preset = YouTube Widescreen HD
The frame rate will be 24 frames per second...if necessary change the frame rate under the Advanced Button/Video Tab
Mobile Phones and Players
with Presets = Apple TV, iPad, iPhone 4 - 720p25
That should give you H.264.mp4 file (1280 x 720 @ 25 progressive frames per second)
Please review and then let us know if any of that worked for you. If not, please more details, including any place where I may have misinterpreted your information.