b+c=21
c+(b+3) = c+b+3 = (b+c)+3 = 21+3 = 24
(c+5)+b = c+5+b = (b+c)+5 = 21+5 = 26
c+(b+6) = c+b+6 = (b+c)+6 = 21+6 = 27
(c+10)+b = c+10+b = (b+c)+10 = 21+10 = 31
c+(b+9) = c+b+9 = (b+c)+9 = 21+9 = 30
(c+15)+b = c+15+b = (b+c)+15 = 21+15 = 36
b+c=21
c+(b+3) = c+b+3 = (b+c)+3 = 21+3 = 24
(c+5)+b = c+5+b = (b+c)+5 = 21+5 = 26
c+(b+6) = c+b+6 = (b+c)+6 = 21+6 = 27
(c+10)+b = c+10+b = (b+c)+10 = 21+10 = 31
c+(b+9) = c+b+9 = (b+c)+9 = 21+9 = 30
(c+15)+b = c+15+b = (b+c)+15 = 21+15 = 36