the answer here is 153
first, use an=a1+d(n-1) with a1= 9, and an=25,
take note that we need odd numbers, therefore, d=2, since there is 2 common difference between 2 odd numbers (i.e. 3, 5 <-- 5-3=2)
solve for n, you have 9
then use
sn=[n(a1+an)] / 2 with n=9, a1= 9, an=25
solv it, youll get 153
