There are several ways to insert a fraction:

In full editor, fraction symbol is available under the menu

Type
frac
inside the full editor and then press SPACE key 
Type
\
and then search for fraction 
Press Alt/
There are several ways to insert a fraction:
In full editor, fraction symbol is available under the menu
Type frac
inside the full editor and then press SPACE key
Type \
and then search for fraction
Press Alt/