\documentclass[12pt]{article}
\usepackage{amsmath, amssymb, graphicx, array, fancyhdr, unicode-math, multirow}

\DeclareMathOperator{\Var}{Var}
\DeclareMathOperator{\sd}{SD}
\DeclareMathOperator{\Pois}{Pois}
\DeclareMathOperator{\Bin}{Bin}
\DeclareMathOperator{\NegBin}{NegBin}
\DeclareMathOperator{\sech}{sech}

% Put this in your preamble (you already load array)
\newcolumntype{C}[1]{>{\centering\arraybackslash}m{#1}}
\newcolumntype{L}[1]{>{\raggedright\arraybackslash}m{#1}}

% Text: Calibri, all bold
\setmainfont{Calibri}
\renewcommand{\seriesdefault}{b}

% Math: choose a math font and visually embolden it
\setmathfont{TeX Gyre Termes Math}                  % base math font
\setmathfont[FakeBold=1.9]{TeX Gyre Termes Math}    % embolden; adjust 1.6–2.4


% set header
\pagestyle{fancy}
\fancyhf{} % clear defaults
\lhead{\resizebox{!}{2cm}{G}}
\chead{\raisebox{0.5cm}{\Huge Introduction}}
\rhead{\resizebox{!}{2cm}{G}}
\setlength{\headheight}{2.5cm} % slightly larger than your 2cm image

% start document
\begin{document}
\thispagestyle{fancy} 

\begin{table}[h!]
\centering
\renewcommand{\arraystretch}{1.2} % a little vertical padding
\begin{tabular}{m{1.2in} m{4in}}
% -------------------- Single --------------
\multirow{3}{*}{\centering\fbox{\includegraphics[width=1in]{images/single.png}}}
  & $A = \{1,2\} = \{n \mid n = 1,2\}$ \\ 
  & $B = \{1,2,3\} = \{n \mid n = 1,2,3\}$ \\ 
  & $C = \{1,2,3,4\} = \{n \mid n = 1,2,3,4\}$ \\ 
  & $X = \{1,2,3,...,n\} = \{n \mid n = 1,2,3,...,n\}$ \\
\\ 
% -------------------- Abstract --------------
\multirow{2}{*}{\centering\fbox{\includegraphics[width=1in]{images/abstract.png}}} 
&$\mathcal{P}(A) = \{\{\emptyset\},\{1\},\{2\},\{1,2\}\}$\\
&$\mathcal{P}(B) = \{\{\emptyset\},\{1\},\{2\},\{3\},\{1,2\,\{1,3\},\{2.3\},\{1,2,3\}\}$\\
&$\mathcal{P}(C) =
\{\,
\emptyset,\,
\{1\},\,
\{2\},\,
\{3\},\,
\{4\},\,
\{1,2\},\,
\{1,3\},\,
\{1,4\},\,$\\
&$\{2,3\},\,
\{2,4\},\,
\{3,4\},\,
\{1,2,3\},\,
\{1,2,4\},\,
\{1,3,4\},\,
\{2,3,4\},\,
\{1,2,3,4\}
\,\}$\\
&$|\mathcal{P}(X)| = 2^n$\\
\\ 
% -------------------- Question --------------
\multirow{3}{*}{\centering\fbox{\includegraphics[width=1in]{images/question.png}}} 
&\\
&$|\mathcal{P}(Z)| = 32$\\
&$|Z| = ?$\\
\\
\end{tabular}
\end{table}

% second page
\newpage
\thispagestyle{fancy}

\begin{table}[h!]
\centering
\renewcommand{\arraystretch}{1.2} % a little vertical padding
\begin{tabular}{m{1.2in} m{4in}}
% -------------------- Answer --------------
\multirow{3}{*}{\centering\fbox{\includegraphics[width=1in]{images/key.png}}} 
&\\
&$|\mathcal{P}(Z)| = 32$\\
&$|Z| = log_2(32) = 5$\\
\\
\end{tabular}

\end{table}

\end{document}