STEP 1 : Convert octal number into binary : (7654.7)8 = (111110101100.111)2 i.e 7=111 , 6=110 go on like this and concate the generated binary string.
STEP 2: make group of 4 binary digits i.e 1111 1010 1100 . 1110 (before "decimal point" make group of 4 binary digits from "right to left" and in the end if some binary digits are remaining just add "0" to make them a group of 4 and after "decimal point" same procedure is done but it is done from "left to right")
STEP 3 : replace the group of binary digits with respected HEX decimal number i.e 1111 = F , 1010 = A , 1100 C , 1110 =E
Answer : (FAC.E)16