x̄ - > Writting Mathematics formulas using LATEX

How to use this method to render brackets and sets (from mathematics)?
I tried these:
![formula](https://render.githubusercontent.com/render/math?math=A%20-%20B%20=%20\{ x%20\in%20\U%20\mid%20x%20\in%20A%20\land%20x%20\notin%20B%20\ } )
![formula](https://render.githubusercontent.com/render/math?math=A,%20B%20\in%20\U,%20x%20\in%20\Z)