Answer:
4.718592
Explanation:
To get to -14.4 from 18 you multiply 18 x 0.8
Repeat that until you get to the 7th term
18 (1st)
18 x 0.8 = -14.4 (2nd)
-14.4 x 0.8 = 11.52 (3rd)
11.52 x 0.8 = 9.216 (4th)
9.216 x 0.8 = 7.3728 (5th)
7.3728 x 0.8 = 5.89824 (6th)
5.89824 x 0.8 = 4.718592 (7th)