Originally Posted by Voodoo

OSAMA
OBAMA

A1 B2 C3 D4 E5 F6 G7 H8 I9 J10 K11 L12 M13 N14 O15 P16 Q17 R18 S19 T20 U21 V22 W23 X24 Y25 Z26

O15S19A1M13A1
O15B2A1M13A1

15+19+1+13+1=49: 4+9=13: 1+3=4;
15+2+1+13+1=32: 3+2=5;
From above: 4+5=9
(9)

There are exactly 10 letters in total between the 2 names, with only 1 letter that is different. 10+1=11;
(11)

From above:
9/11