Shutoff valve water leak
I am experiencing a leak from an interior plumping shutoff valve (only when it is open), and I'm not sure what to do to fix it. Youtube videos and online searches seemed to suggest different remedies, including repacking the valve, but my shutoff valve only seems to have one nut on it. Does anyone know the best way to address the leak (it's through the stem)? IA photo of the valve is below; it's an interior valve, but I have an exterior valve that looks the same, so I've included a photo of that as well because it's easier to photograph. Thanks in advance for any help- I'd like to be able to shut off the main water supply and get it fixed without any headaches or having to call a plumber, and the first step to doing that is knowing exactly what I need to do!