Alright, this is a tricky and time consuming one

R = Red
Y = Yellow
G = Green

Sequence: R, Y, G

Stmt 1) The 18th tile in the row is not yellow.
Two possibilities:

A) 18 19 20 21 22 23 24
----G R Y G R Y G

B) 18 19 20 21 22 23 24
----R Y G R Y G R

Hence not sufficient

Stmt 2) The 19th tile in the row is not green.
Two possibilities:

A) 18 19 20 21 22 23 24
---- R Y G R Y G R

B) 18 19 20 21 22 23 24
---- G R Y G R Y G

Hence stmt 2 not sufficient as well.

Combining both statements:

18 Not Yellow and 19 not Green
Two possibilities, again:

A) 18 19 20 21 22 23 24
---- R Y G R Y G R

B) 18 19 20 21 22 23 24
---- G R Y G R Y G

Hence answer is E.

What do you understand with preceded, I set this order GYR - R is preceded by yellow and yellow is preceded by Green.

Another imp. thing which is not there in question is which tile preceed green; means RYGGGGGGGGGGGGG is also a valid tile arrangement.
Keeping this is mind, E is the only valid answer.

My bad.
Thanks for correcting!

OA E

shouldnt the answer be C??
as it says preceded the sequence would be GYRGYR
as 19th cannot be G, combining with (A) we get 18th as G and 19th as Y