Answer is = 51

6 + 3 = 9 9 + 6 = 15 15 + 12 = 27

i.e. we add 3 , 6 , 12 , 24 , 48 , 96..................to find the next turm

Another logic is 6, 9 (6+3), 15 (9+6), 27 (15+12), 51 (27+24)

So the answer is 51

Next number is 45. 6, 9 (6+3), 15 (9+6), 27 (15+12), 45 (27+18)

Answer is 33

since

2*3=6 3*3=9 => (2+1)*3=9 5*3=15 => (3+2)*3=15 9*3=27 => (5+4)*3=27 11*3=33