Which formula represents Average Velocity?

$v_{\text{a}\text{v}\text{g}}=\frac{s}{}t$

$v_{\text{a}\text{v}\text{g}}\frac{v_2-v_1}{t_2-t_1}$

$v=d\frac{s}{d}t$

$v_{\text{a}\text{v}\text{g}}=v_0+at$