How can I plot the functions
P=20-1/5*Q and P=5+1/9*Q
so as to find the equilibrium point?
The figure I need is like the following:
Furthermore, how could I put the equation on each line?
My unfinished so far code is:
\documentclass{article}
\usepackage[english,greek]{babel}
\usepackage{ucs}
\usepackage[utf8x]{inputenc}
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage{tikz}
\usepackage{tkz-tab}
\usepackage{latexsym}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amsthm}
\usepackage{graphicx}
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage{color}
\usepackage{tkz-euclide}
\usetikzlibrary{shapes.geometric}
\usepackage{tkz-fct} \usetkzobj{all}
\usetikzlibrary{calc,decorations.pathreplacing}
\usetikzlibrary{decorations.markings}
\usepackage{pgfplots}
\usepackage{verbatim}
\usepackage{smartdiagram}
\usesmartdiagramlibrary{additions}
\usepackage{tikz}
\usetikzlibrary{arrows}
\usetikzlibrary{intersections}
\begin{document}
\begin{center}
\begin{tikzpicture}
\begin{axis}[ axis x line=bottom, xtickmax=100, ytickmin=0, ymin=0, enlargelimits=false ]
\addplot[blue,mark=none, domain=-4:4,samples=20] {20-x/5};
\end{axis}
\end{tikzpicture}
\end{center}
\end{document}