Originally Posted by: Jay Pham

How do I mute the E A D strings?[/quote][p]First, you want to avoid picking them at all. Next, mute with the palm of your picking hand.

I cover muting lower strings with the picking hand here.

https://www.guitartricks.com/lesson.php?input=27242&s_id=2281

[quote=Jay Pham]For the first chord, I bar the whole 9th fret G B E with my index, 10th fret of the B string with my middle, 12th fret of the E string with my pinky.

You might just be making it more difficult. It's usually easier to just barre the 3 strings you are playing. Then mute the lower strings with your picking hand palm.

Hope that helps!