As given arithmetic sequence is :-
-17 , -13 , -9
So, here we have to find a12
a ( 1st term ) = -17
d ( common difference) = a2 - a1
d = -13 -(-17)
d = 4
nth place = a12
Now we know that to find any term we apply formula :-
an = a + (n-1)d
So putting Values in above mentioned formula :-
a12 = -17 + ( 12-1) 4
a12 = -17 + (11)4
a12 = -17 + 44
a12 = 27
Hope it helps