#### Answer

The system of equations is:
x - 2y = 4
y = -1
The variables are:
x = 2
y = -1

#### Work Step by Step

The matrix is represented by the following system of equations:
x - 2y = 4
y = -1
Using back substitution to solve the system:
x - 2(-1) = 4
x + 2 = 4
x = 2
The variables are:
x = 2
y = -1