Chapter 2: Linear Equations
2.8 The Mystery X Puzzle
The centre number of each square is found by using the order of operations on the numbers that surround it. The challenge is to solve for the variable 
![\[\begin{tabular}{|c|c|c|} \hline \begin{array}{ccc}&5& \\ \\ &\textbf{21}& \\ \\ 3&&6\end{array}& \begin{array}{ccc}&3& \\ \\ &\textbf{42}& \\ \\ 11&&9\end{array}& \begin{array}{ccc}&12& \\ \\ &\textbf{64}& \\ \\ 5&&X\end{array}\\ \hline \end{tabular}\]](https://pressbooks.bccampus.ca/intermediatealgebrakpu/wp-content/ql-cache/quicklatex.com-c2bc24da5f8d7a779fcefdf75062420f_l3.png "Rendered by QuickLaTeX.com")
Can you solve for 
? Can you find any other possible solution?
