Find the last number in the given sequence

Question

Find the last number in the given sequence $$\begin{pmatrix} 4& 9& 20\\ 8& 5& 14\\ 10& 3& ?\end{pmatrix}$$

(It's $3\times3$ matrix)

Answer 1

The answer is $11$ since then $3 r_2 -r_1=2 r_3$ where $r_1, r_2, r_3$ are the three rows.

Answer 2

One possibility is

$$\begin{pmatrix} 4& 9\\ 8& 5\\ 10& 3\end{pmatrix} \begin{pmatrix} 1& 0& \tfrac12\\ 0& 1& 2\end{pmatrix}$$