\begin{align*} x&=y & w &=z & a&=b+c\\ 2x&=-y & 3w&=\frac{1}{2}z & a&=b\\ -4 + 5x&=2+y & w+2&=-1+w & ab&=cb \end{align*}
\begin{align} (a+b)^2 &= (a+b)(a+b) \\ &= a^2+2ab+b^2 \end{align}