$$\begin{aligned} & A = \left[ \begin{array} { l l } 2 & 3 \\ 1 & 2 \end{array} \right] \\ & B = \left[ \begin{array} { l l } 1 & 2 \\ 0 & 5 \end{array} \right] \end{aligned}$$
With the matrix notation
$$( 2 A - B ) \cdot \left[ \begin{array} { l } x \\ y \end{array} \right] = \left[ \begin{array} { l } 1 \\ 0 \end{array} \right]$$
Which of the following is the system of linear equations?
A) $\begin{aligned} & x - 4 y = 0 \\ & 2 x - y = 1 \end{aligned}$
B) $\begin{aligned} & x + 2 y = 0 \\ & 2 x - 3 y = 1 \end{aligned}$
C) $\begin{aligned} & 2 x + y = 1 \\ & x - y = 0 \end{aligned}$
D) $\begin{aligned} & 3 x - 2 y = 1 \\ & 2 x + y = 0 \end{aligned}$
E) $\begin{aligned} & 3 x + 4 y = 1 \\ & 2 x - y = 0 \end{aligned}$

Let I be the $2 \times 2$ identity matrix and
$$A = \left[ \begin{array} { l l } 4 & 5 \\ 1 & 3 \end{array} \right]$$
Accordingly, which of the following is $( \mathbf { A } - \mathbf { I } ) ^ { - \mathbf { 1 } }$ equal to?
A) $\left[ \begin{array} { r r } 2 & - 5 \\ - 1 & 3 \end{array} \right]$
B) $\left[ \begin{array} { r r } 1 & - 4 \\ - 2 & 3 \end{array} \right]$
C) $\left[ \begin{array} { r r } 0 & - 1 \\ - 1 & 4 \end{array} \right]$
D) $\left[ \begin{array} { l l } - 2 & 5 \\ - 1 & 0 \end{array} \right]$
E) $\left[ \begin{array} { l l } 2 & - 5 \\ 0 & - 3 \end{array} \right]$

Let $A$ and $B$ be $2 \times 1$ matrices and $t$ be a variable such that for all $x$ and $y$ values satisfying
$$x - y = 3$$
we have
$$\left[ \begin{array} { l } x \\ y \end{array} \right] = t A + B$$
Accordingly, which of the following could matrices A and B be, respectively?
A) $\left[ \begin{array} { l } 1 \\ 0 \end{array} \right] , \left[ \begin{array} { l } 3 \\ 0 \end{array} \right]$
B) $\left[ \begin{array} { l } 0 \\ 1 \end{array} \right] , \left[ \begin{array} { l } 3 \\ 0 \end{array} \right]$
C) $\left[ \begin{array} { l } 1 \\ 1 \end{array} \right] , \left[ \begin{array} { l } 3 \\ 1 \end{array} \right]$
D) $\left[ \begin{array} { l } 1 \\ 1 \end{array} \right] , \left[ \begin{array} { l } 3 \\ 0 \end{array} \right]$
E) $\left[ \begin{array} { l } 1 \\ 1 \end{array} \right] , \left[ \begin{array} { r } 3 \\ - 3 \end{array} \right]$

The inverse of matrix A is $A ^ { - 1 } = \left[ \begin{array} { l l } 1 & 0 \\ 2 & 1 \end{array} \right]$. Given that
$$A \cdot \left[ \begin{array} { l } 1 \\ a \end{array} \right] = \left[ \begin{array} { l } b \\ 4 \end{array} \right]$$
what is the sum $\mathrm { a } + \mathrm { b }$?
A) 5
B) 7
C) 8
D) 9
E) 11

$$3 x - y = 2$$ $$5 x + 2 y = 3$$
The matrix representation of the linear equation system is
$$A \cdot \left[ \begin{array} { l } x \\ y \end{array} \right] = \left[ \begin{array} { l } 2 \\ 3 \end{array} \right]$$
Given that
$$A \cdot \left[ \begin{array} { l } 1 \\ 2 \end{array} \right] = \left[ \begin{array} { l } a \\ b \end{array} \right]$$
what is the sum $\mathbf { a + b }$?
A) 4
B) 6
C) 8
D) 10
E) 12