"Teacher B is older than the art teacher" = = = The teacher may teach music and calligraphy.
The art teacher is younger than Mr. C' = = > Mr. C may teach music and calligraphy.
= = = = = = & gt； Teachers B and C teach music and calligraphy. So Teacher A teaches art. ..
Teacher b is older than the art teacher, and the teacher who teaches art is younger than teacher C.
= = = = = = & gt； Beauty (1). C > beauty (1).
"Teacher A is older than the teacher who teaches music = = = > A (America) > Music teacher
= = = = = = & gt； Beauty (1). C > beauty (1). A (American) music teacher
If there is any contradiction, we can only conclude that A teaches art..