Code copied from Problem with formatting tables with equal column widths which had double backslashes trashed in earlier update.
\begin{table}[h]
\caption{Distribution of mappings for the SLA parameter $\pi$.}
\label{tab:distPi} \centering
\begin{tabular*}{0.45\textwidth}{@{\extracolsep{\fill}}|c|c|c|}
\hline
\multicolumn{3}{|c|}{\textbf{Name of the SLA parameter $\pi$}} \\
\hline
\emph{Cost} & \emph{Charge} & \emph{Rate} \\
\hline
15\% & 15\% & 40\% \\
\hline
\hline
\multicolumn{3}{|c|}{\textbf{Unit of the SLA parameter $\pi$}} \\
\hline
\emph{USD} & \emph{GBP} & \emph{YPI} \\
\hline
38\% & 2\% & 40\% \\
\hline
\end{tabular*}
\vspace{-0.3cm}
\end{table}
and this is how I've made the second table:
\begin{table}[h]
\caption{Distribution of mappings for the SLA parameter $\mu$.}
\label{tab:distMu} \centering
\begin{tabular*}{0.45\textwidth}{@{\extracolsep{\fill}}|c|c|c|c|c|c|}
\hline
\multicolumn{6}{|c|}{\textbf{Name of the SLA parameter $\mu$}} \\
\hline
\multicolumn{3}{|c|}{\emph{MemoryConsumption}} & \multicolumn{3}{|c|}{\emph{Consumption}} \\
\hline
\multicolumn{3}{|c|}{70\%} & \multicolumn{3}{|c|}{30\%} \\
\hline
\hline
\multicolumn{6}{|c|}{\textbf{Unit of the SLA parameter $\mu$}} \\
\hline
\multicolumn{2}{|c|}{\emph{Mbit}} & \multicolumn{2}{|c|}{\emph{Gbit}} & \multicolumn{2}{|c|}{\emph{Tbit}} \\
\hline
\multicolumn{2}{|c|}{5\%} & \multicolumn{2}{|c|}{55\%} & \multicolumn{2}{|c|}{40\%} \\
\hline
\end{tabular*}
\vspace{-0.3cm}
\end{table}