U3=800 U27=204800 a....? r...?

U3 = ar^2 = 800
U7 = ar^6 = 204800

U7/U3 = ar^6 / ar^2 = 204800/800
= r^4 = 256
= r = 4

U3 = ar^2 = 800
U3 = a.16 = 800
U3 = a = 50

Sori ya kalo salah