Answer
See explabation
Work Step by Step
\[
\begin{array}{l}
A=\left[\begin{array}{ll}
6 & 9 \\
4 & 5
\end{array}\right] \\
{\left[\begin{array}{ll}
6 & 9 \\
0 & -1
\end{array}\right]=U} \\
R_{2}=R_{2}-\frac{21}{3} R_{1} \\
L=\left[\begin{array}{cc}
1 & 2 \\
2 / 3 & 1
\end{array}\right]
\end{array}
\]
Element (1,2) can be found using factor used above
\[
\frac{R_{21}}{R_{11}}=\frac{2}{3}
\]
Diagonal elements will be 1
