Question 855462
Firstly we have to find sequence,
3,9,15,21,............,45, this sequence is in AP.
a=3, d=6, Tn=45, n=?
Tn = a +  (n-1)d
45 =3 +  (n-1)6
45 =3 + 6n-6
45 =6n - 3
45 + 3 =6n
48 = 6n
n =48/6
n = 8. 
8 odd numbers less than 50 divisible by 3