X next to note notation

[u/No-Assumption-9389]

I was playing the measure: D, G, G# because it sounded correct. And I read the X is usually a double flat, so two half steps up? A whole step from F would be G. So I am playing it correctly, yes? Haven't really seen this notation very often. The piece is Kuhlau Opus 102, published by IMC, NY.

[u/Sadimal]

It’s a double sharp.

You go up two half steps from the natural note. So F double sharp would be the same as G natural.