\documentclass{article}

\begin{document}

\begin{tabular}{cccccc}%Begin Table 1
%creates a table with 6 columns, each of which contains entries that are centered
$x$ & 1 & 2 & 3 & 4 & 5 \\ 
%Using & forces a column break and \\ forces a line break
$f(x)$ & 10 & 11 & 12 & 13 & 14
\end{tabular}%End Table 1

The table below has a horizontal line between the first and second row and the entries are right justified:\\
\begin{tabular}{rrrrrr}%Begin Table 2
%Entries are right justified
$x$ & 1 & 2 & 3 & 4 & 5 \\ \hline %inserts a horizontal line after this row
$f(x)$ & 10 & 11 & 12 & 13 & 14
\end{tabular}%End Table 2

The table below has verticle bars separating the columns.A double bar separates the first and second column.\\
\begin{tabular}{c||c|c|c|c|c}
%inserts verticle lines between columns
$x$ & 1 & 2 & 3 & 4 & 5 \\ \hline
$f(x)$ & 10 & 11 & 12 & 13 & 14
\end{tabular}

\begin{eqnarray}
%Automatically enters MATH MODE, so $$ not necessary
50 &=& 5.48 \sqrt{d} \\ %Blank lines within the equation environment may cause compiling errors.
\frac{50}{5.48} &\approx& 9.1241 = \sqrt{d} \\
d &=& {9.1241}^2 = 83.325
\end{eqnarray}

\begin{eqnarray*}%Using the asterisk removes automatic equation line numbering
50 &=& 5.48 \sqrt{d} \\
\frac{50}{5.48} &\approx& 9.1241 = \sqrt{d} \\
d &=& {9.1241}^2 = 83.325
\end{eqnarray*}

\end{document}