1. Which ordered pair is a solution to the system of equations $$\begin{cases} x - 2y = 6 \\ 3x + y = 4 \end{cases}$$?
2. The ordered pair $(3, b)$ is a solution to the system of equations $$\begin{cases} x + y = 5 \\ 2x - y = 4 \end{cases}$$. What is the value of $b$? ___
3. Is the ordered pair $(4, -1)$ a solution to the system of equations $$\begin{cases} 2x + y = 7 \\ x - y = -1 \end{cases}$$?
4. The ordered pair $(1, 5)$ is tested as a solution for the system $$\begin{cases} y = 3x + 2 \\ y = -2x + 7 \end{cases}$$. It satisfies the first equation. When substituted into the second equation, $y$ evaluates to ___.
5. Why is the ordered pair $(1, 1)$ not a solution to the system of equations $$\begin{cases} 4x - y = 3 \\ x + y = 1 \end{cases}$$?
6. Which of the following pairs of equations forms a system of linear equations?
7. A system of equations is given by $C = 25h + 80$ and $C = 30h + 60$. What pair of variables is used in this system?
8. Two friends are saving money. Sarah's savings are modeled by $A = 10w + 50$. Ben's savings are modeled by $A = 15w + 25$. Together, these two equations form a ___ of linear equations.
9. Is the following statement true or false? "A system of linear equations must consist of two equations that use different variables."