Answer:
Common difference = 0.5
First term = 6.
Explanation:
the 12th term a12 = a1 + d(12-1) where a1 = first term and d = the common difference.
So a1 + 11d = 10.5 ....(A) Similarly:
a1 + 17d = 13.5....(B)
Subtracting equations:
(B) - (A) :-
6d = 13.5 - 10.5 = 3
d = 3/6 = 0.5
From equation (A):
a1 + 11(0.5) = 10.5
a1 = 10.5 -5.5 = 5.