Here,
Let the first term be denoted by a and commom difference by b.
Now,
T1 = a
= 7/9
T13 = a + 12 d
or, 4/5 = 7/9 + 12d
or 12d = 4/5 -7/9
or, 12d = 1/45
or, d = 1/410.
then,
T7= a + 6d
= 7/9 + 1/410
= 2879/2870
Please check the answer and tell me whether it is correct or not.
