ANSWERS

1. students x | x's GPA is better than 3.5 ~(x studies a lot.)
   There are some students whose GPA's are better than 3.5 and they don't study a lot.
   
   
2. polygons p | p has 3 sides ~(p is a triangle)
   There exists a polygon such that the polygon has 3 sides and it is not a triangle.
   
   
3. numbers n | n is real ~(n² is positive.)
   There are some numbers n such that n is real and n² is not positive.
   
   
4. girls g | g dates that guy and ~(g is crazy)
   There are some girls who date that guy and who are not crazy.