I'm using a query and need strip out data.
Here is an example of the data I have to work with:

85123147/RS08
85123147W/RS08
TEX-M/SS09

I need my query to strip off everything after & including the "/" so
that I get the following results.

85123147
85123147W
TEX-M

Do I accomplish this using the INSTR function and if so how would it
work?

I would appreciate some guidance.
Thank you!