\begin{table}[htbp!]
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{lcrX}
\relax   left  &  center  &  right  &  justify  \\
\hline
\relax   lefted  &   centered  &  righted  &  justified body with long line  \\
\hline
\relax   foot left  &  centerf foot  &  right foot  &  justify footer  \\
\end{tabularx}

\caption[]{this is the legend}
\end{minipage}
\end{table}

\begin{table}[htbp!]
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{XX}
\relax  First Header   &  Second Header   \\
\hline
\relax  Content Cell   &  Content Cell    \\
\relax  Content Cell   &  Content Cell    \\
\end{tabularx}

\caption[]{legend}
\end{minipage}
\end{table}

\bigskip
\noindent
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{XX}
\relax  First Header   &  Second Header   \\
\hline
\relax  Content Cell   &  Content Cell    \\
\relax  Content Cell   &  Content Cell    \\
\end{tabularx}
\end{minipage}
\bigskip

\bigskip
\noindent
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{XX}
\relax    First Header   &  Second Header   \\
\hline
\relax                   &  Content Cell    \\
\relax    Content Cell   &  Content Cell    \\
\end{tabularx}
\end{minipage}
\bigskip

\bigskip
\noindent
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{XX}
\relax    First Header   &  Second Header  \\
\hline
\relax                   &  Content Cell  \\
\relax    Content Cell   &    \\
\end{tabularx}
\end{minipage}
\bigskip

\begin{table}[htbp!]
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{crl}
\relax    First Header   &  Second Header (Right)  &  Third (Left)  \\
\hline
\relax                   &  Content Cell   &    \\
\relax    Content Cell (Centered)   &                 &  Here  \\
\relax    x   &                 &  Here  \\
\hline
\relax    Footer  &   &    \\
\end{tabularx}

\caption[]{legend}
\end{minipage}
\end{table}


\begin{alltt}
   First Header  \textbar{} Second Header (Right) \textbar{} Third (Left)
   :-----------: \textbar{} ------------: \textbar{} :----
                 \textbar{} Content Cell  \textbar{}
   Content Cell (Centered)  \textbar{}               \textbar{} Here
   x  \textbar{}               \textbar{} Here
   Footer \textbar{}\textbar{}\textbar{}
   \textbar{}+ legend +\textbar{}


\textbar{} First Header  \textbar{} Second Header \textbar{}
\textbar{} ------------- \textbar{} ------------- \textbar{}
\textbar{} Content Cell  \textbar{} Content Cell  \textbar{}
\textbar{} Content Cell  \textbar{} Content Cell  \textbar{}
\textbar{}+ legend +\textbar{}
\end{alltt}

\bigskip
\noindent
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{XccccccX}
\relax  ~  &  100  &   200  &   300  &  400  &  500 &  \dots{}  &  ~   \\
\relax  ~  &  3  &  6  &  9  &  12  &  15  &  \dots{}  &  ~   \\
\end{tabularx}
\end{minipage}
\bigskip

\bigskip
\noindent
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{p{0.30\textwidth}p{0.30\textwidth}}
\relax  30\% and   &  30 \%   \\
\end{tabularx}
\end{minipage}
\bigskip

\bigskip
\noindent
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{Xp{0.30\textwidth}}
\relax  70\% and   &  30 \%   \\
\end{tabularx}
\end{minipage}
\bigskip

\bigskip
\noindent
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{XX}
\relax  50\% and   &  50 \%   \\
\end{tabularx}
\end{minipage}
\bigskip

\bigskip
\noindent
 \begin{minipage}[t]{\textwidth}
\begin{tabularx}{\textwidth}{crlp{0.20\textwidth}p{0.10\textwidth}X}
\relax  center     &  right  &  left    &   20\%      &       10\%  &  rest      \\
\end{tabularx}
\end{minipage}
\bigskip