https://s0.wp.com/latex.php?latex=%5Cdisplaystyle+P%5BX%3Dx+%5Clvert+Z%3Dz%5D%3D%5Cfrac%7B%5Cdisplaystyle+%5Cbinom%7Bn%7D%7Bx%7D+%5Cbinom%7Bm%7D%7Bz-x%7D%7D%7B%5Cdisplaystyle+%5Cbinom%7Bn%2Bm%7D%7Bz%7D%7D&bg=ffffff&fg=333333&s=-1