The / sign suffices as the fraction sign. Writing 1/2 is the same as writing $${\frac{{\mathtt{1}}}{{\mathtt{2}}}}$$.
There isn't one. Let's say you want to write one-thirds. You would write it 1/3, or one divided by three.
The / sign suffices as the fraction sign. Writing 1/2 is the same as writing $${\frac{{\mathtt{1}}}{{\mathtt{2}}}}$$.