Hi! i don't get this problem... I was wondering if you could help.
The problem is:
x-y=9
3x+(y+4)=51
What is S and what is L?
I have no idea what S & L are; the terms do no appear in your equation. They may be abbreviations for something the teacher wants you to do.
By substituting x-9 for y in the second equation, you can solve for x.