Align

\[\begin{align*} 2x - 5y &= 8 \\ 3x + 9y &= -12 \end{align*}\]

\[\begin{align} v&=\frac{dp}{dt} \\ &= \lim_{t_2 \to t_1} \frac{p_2-p_1}{t_2-t_1} \end{align}\]