We have that
1/3 = 7/9 + d (13 - 1)
1/3 = 7/9 + 12d
(1/3 - 7/9) =12 d
(3/9 - 7/9) = 12 d
-4/9 = 12 d divide both sides by 12
-4/ 9 * 1/12 = d
-4/108 =d
-1/27 = d
To find the seventh term we have
7/9 + (-1/27) (7 -1)
7/9 + (-1/27) (6)
7/9 -6/27 =
7/9 - 2/9 =
5/9
