ok use why they told you.
17=A+B+C & A=B-3 &C=2+B
we only what to work with one variable at a time.
lucky for us we have an idea of what "A" & "C" are. we can plug those into our first equation respectively.
SOLVE FOR B
17= (B-3)+B+(2+B)
17=B-3+B+2+B
17=3B-1
17+1=3B
18=3B
18/3=B
6=B (this means he won 6 B titles)
SOLVE FOR A
A=B-3
A=6-3
A=3
SOLVE FOR C
C=2+B
C=2+6
C=8
CHECK
17=A+B+C
17=3+6+8
17=17