Let's solve each system of linear equations using the
elimination method. The goal is to eliminate one variable by adding or subtracting the equations, then solve for the remaining variable.
---
System 1:
$$
\begin{align*}
(1)\quad & 2x + 3y = -12 \\
(2)\quad & -x - 3y = 18
\end{align*}
$$
Step 1: Add the two equations to eliminate $ y $:
$$
(2x + 3y) + (-x - 3y) = -12 + 18
$$
$$
(2x - x) + (3y - 3y) = 6
$$
$$
x = 6
$$
Step 2: Substitute $ x = 6 $ into equation (1):
$$
2(6) + 3y = -12 \Rightarrow 12 + 3y = -12
\Rightarrow 3y = -24 \Rightarrow y = -8
$$
✔ Solution: $ x = 6, y = -8 $
---
System 2:
$$
\begin{align*}
(1)\quad & x + 3y = 18 \\
(2)\quad & -x - 4y = -25
\end{align*}
$$
Step 1: Add the two equations to eliminate $ x $:
$$
(x + 3y) + (-x - 4y) = 18 + (-25)
\Rightarrow (x - x) + (3y - 4y) = -7
\Rightarrow -y = -7 \Rightarrow y = 7
$$
Step 2: Plug $ y = 7 $ into equation (1):
$$
x + 3(7) = 18 \Rightarrow x + 21 = 18 \Rightarrow x = -3
$$
✔ Solution: $ x = -3, y = 7 $
---
System 3:
$$
\begin{align*}
(1)\quad & x - y = 11 \\
(2)\quad & 2x + y = 19
\end{align*}
$$
Step 1: Add equations to eliminate $ y $:
$$
(x - y) + (2x + y) = 11 + 19
\Rightarrow 3x = 30 \Rightarrow x = 10
$$
Step 2: Plug $ x = 10 $ into equation (1):
$$
10 - y = 11 \Rightarrow -y = 1 \Rightarrow y = -1
$$
✔ Solution: $ x = 10, y = -1 $
---
System 4:
$$
\begin{align*}
(1)\quad & -6x + 5y = 1 \\
(2)\quad & 6x + 4y = -10
\end{align*}
$$
Step 1: Add the equations to eliminate $ x $:
$$
(-6x + 5y) + (6x + 4y) = 1 + (-10)
\Rightarrow 0x + 9y = -9 \Rightarrow y = -1
$$
Step 2: Plug $ y = -1 $ into equation (1):
$$
-6x + 5(-1) = 1 \Rightarrow -6x - 5 = 1 \Rightarrow -6x = 6 \Rightarrow x = -1
$$
✔ Solution: $ x = -1, y = -1 $
---
System 5:
$$
\begin{align*}
(1)\quad & 7x - y = -10 \\
(2)\quad & -7x + 5y = -6
\end{align*}
$$
Step 1: Add equations to eliminate $ x $:
$$
(7x - y) + (-7x + 5y) = -10 + (-6)
\Rightarrow 0x + 4y = -16 \Rightarrow y = -4
$$
Step 2: Plug $ y = -4 $ into equation (1):
$$
7x - (-4) = -10 \Rightarrow 7x + 4 = -10 \Rightarrow 7x = -14 \Rightarrow x = -2
$$
✔ Solution: $ x = -2, y = -4 $
---
System 6:
$$
\begin{align*}
(1)\quad & -7x - y = 13 \\
(2)\quad & 8x + y = -14
\end{align*}
$$
Step 1: Add equations to eliminate $ y $:
$$
(-7x - y) + (8x + y) = 13 + (-14)
\Rightarrow x = -1
$$
Step 2: Plug $ x = -1 $ into equation (2):
$$
8(-1) + y = -14 \Rightarrow -8 + y = -14 \Rightarrow y = -6
$$
✔ Solution: $ x = -1, y = -6 $
---
✔ Final Answers:
| System | Solution |
|-------|---------|
| 1 | $ x = 6, y = -8 $ |
| 2 | $ x = -3, y = 7 $ |
| 3 | $ x = 10, y = -1 $ |
| 4 | $ x = -1, y = -1 $ |
| 5 | $ x = -2, y = -4 $ |
| 6 | $ x = -1, y = -6 $ |
Let me know if you'd like a visual explanation or graphing!
Parent Tip: Review the logic above to help your child master the concept of systems of equations elimination worksheet.