3r-6=-21
3r-6+6=-21+6 (Add 6 to both sides...)
3r=-15
r=-5
3r-6=21
3r-6+6=21+6 (Add 6 to both sides...)
3r=27
r=9
r=-5 or r=9
R=9 this is the answer to the question
They are most likely to advertise the APR
5, 3, -5, -1
-2x-1 = 2+3= 5
-2x0 = 0+3= 3
-2x1 = -2+3= -5
-2x2 = -4+3= -1
