Answer
$a=12,b=-4,c=10$
Work Step by Step
Plugging in $x=-1,y=2,z=-3$ into the equations we can easily obtain the constants, since there must be an equality between the two sides.
Hence: $1(-1)+2(2)-3(-3)=-1+4+9=12=a$
$-(-1)-2+1(-3)=1-2-3=-4=b$
$2(-1)+3(2)-2(-3)=-2+6+6=10=c$