Microsoft Office Equation Field

Overstrike In Fraction Equation

1. Go to Insert > Quick Parts > Field
   
   
   
   
   
2. In the "Field names" list, select Eq 
3. Click "Fields Codes" button.
4. In then "Fields codes:" box, type this:
5. {EQ \f(18,12) = \f(\o(18,\\) : 6,\o(12,\\) : 6) = \f(3,2)}
6. And then select OK button.