x + y = 4 {\displaystyle x+y=4}
x − y = 2 {\displaystyle x-y=2} | x y h z v i | {\displaystyle {\begin{vmatrix}x&y&h\\z&v&i\end{vmatrix}}}
the revenu is 500,000
a 2 + b 4 = 2 {\displaystyle a^{2}+b^{4}=2}
