fix

nafems4.md

@@ -856,7 +856,7 @@ Without resorting into philosophical digressions about the difference between [f
 
 So you do not how to program and th
 
-open source! not about price,  free \neq gratis, it is about freedom in spanish this would be easier
+open source! not about price,  free $\neq$ gratis, it is about freedom in spanish this would be easier
 
 que hacen los programas? NADIE SABE