Just download dotnetfx35installer.exe and run it. That's it.
You don't need the installation media. It's packaged in the executable!
Fixes Errors
0x800704220x800F09500x800F0922
Probably Fixes
0x800F09060x800F081F0x800F0907
It seems like quite a few people have an issue installing the Dotnet Framework 3.5.
I was one of them. All the guides on how to fix this said to just download a new
Windows ISO and grab the required installation files and use DISM to load it into
Windows 10. Well, that's dumb. I'm not going to wait two hours just to take a
couple of files out of the ISO. Spoiler: I did. So here are the files that you need
to install Dotnet Framework 3.5. I'm not really sure about how legal this is to
be redistributing these so don't hurt me, Microsoft. I'm really just trying to help
out here. I'm not stealing anyone's data and I'm not making any money off of this
redistribution.
I hope this ends up helping someone.