문제: 다음 연립방정식을 풀어라.

\[
\left\{\begin{array}{l}
x-y=-3\\
2x-y=3
\end{array}\right.
\]

tikz/tzplot으로 다음과 같이 풀었습니다.

\begin{tikzpicture}[scale=.4]
\tzhelplines(10,12)
\tzaxes(-3,-3)(10,12){$x$}{$y$}
\def\Fx{3+\x}
\def\Gx{-3+2*\x}
\tzfn"A"\Fx[-2:8]{$f(x)=x+3$}[br]
\tzfn"B"\Gx[.5:7]{$g(x)=2x-3$}[a]
\tzXpoint{A}{B}(E){$P$}[al]
\tzgetxyval(E){\Ex}{\Ey}
\tzproj*(E){\Ex}{\Ey}
\end{tikzpicture}