Question 251009
<pre>
1.  O & I
2.  O -> (S v G)
3.  I -> ~G                / :. S
---------------------- 
4.  I & O                  1     Commutation
5.  O                      1     Simplification
6.  I                      4     Simplification
7.  ~G                     3,6   Modus Ponens
8.  S v G                  2,5   Modus Ponens
9.  S                      8,7   Disjunctive Syllogism
</pre>