1) The general English alphabet series:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
2) The arrangement of English alphabets according to the given order:
Left End D C B A I H G F E O N M L K J V U T S R Q P W X Y Z Right End
3) 8th letter from the right End: S
4) Then 7th letter to the left of S is,
D C B A I H G F E O N M L K J V U T S R Q P W X Y Z
Hence, 7th letter to the left of the 8th letter from the right end is M.