\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}{F}}
\chead{\raisebox{0.5cm}{\Huge Introduction}}
\rhead{\resizebox{!}{2cm}{F}}
\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}}} 
  & $S = \{"H","T"\}$ \\ 
  & $T = \{"H","T"\}$ \\ 
  &\\
\\
\\
% -------------------- Abstract --------------
\multirow{2}{*}{\centering\fbox{\includegraphics[width=1in]{images/abstract.png}}} 
  & $S * T = \{\{"H","H"\},\{"H","T"\},\{"T","H"\},\{"T","T"\},\}$\\
  & $|S * T| = |S| * |T| = 4 $\\
  &\\
  &\\
\\
% -------------------- Question --------------
\multirow{3}{*}{\centering\fbox{\includegraphics[width=1in]{images/question.png}}} 
  & $A = \{"H","T"\}$ \\
  & $B = \{1, 2, 3, 4, 5, 6\}$ \\
  & $A * B = ?$ \\
  & $|A * B| = ?$ \\
\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}}} 
  & $A = \{"H","T"\}$ \\
  & $B = \{1, 2, 3, 4, 5, 6\}$ \\
  & $A * B = \{   \{"H",1\},\{"H",2\},\{"H",3\},\{"H",4\},\{"H",5\},\{"H",6\},$\\
& $\{"T",1\},\{"T",2\},\{"T",3\},\{"T",4\},\{"T",5\},\{"T",6\}  \}$ \\
  & $|A * B| = |A| * |B| = 2 * 6 = 12$ \\
\end{tabular}
\end{table}



\end{document}
