Answer:
114
Step-by-step explanation:
The first term (a1) = 1 + 3 = 4 (substituting 1 for i)
The last term (L) = 12 + 3 = 15
So the sum of the 12 terms = (n/2)(a1 + L)
= (12/2) (4 + 15)
= 6 * 19
= 114 (answer)
114 so D is the correct choice
