Let’s solve each system of equations using the
elimination method — that means we’ll add or subtract the equations to cancel out one variable, then solve for the other.
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Problem 1:
Equations:
2x + 2y = -2
3x - 2y = 12
Notice: The y terms are
+2y and
-2y → they are opposites! So if we
add the two equations, the y’s will cancel.
Add them:
(2x + 3x) + (2y - 2y) = -2 + 12
→ 5x + 0 = 10
→ 5x = 10
→ x = 2
Now plug x = 2 into one of the original equations. Let’s use the first one:
2x + 2y = -2
2(2) + 2y = -2
4 + 2y = -2
2y = -6
y = -3
✔ Solution:
(2, -3)
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Problem 2:
Equations:
4x - 2y = -1
-4x + 4y = -2
Look at the x terms:
+4x and
-4x → perfect! Add the equations to eliminate x.
Add them:
(4x - 4x) + (-2y + 4y) = -1 + (-2)
→ 0 + 2y = -3
→ 2y = -3
→ y = -3/2 or -1.5
Now plug y = -3/2 into the first equation:
4x - 2(-3/2) = -1
4x + 3 = -1
4x = -4
x = -1
✔ Solution:
(-1, -3/2) or
(-1, -1.5)
*(We can write it as a fraction unless told otherwise.)*
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Problem 3:
Equations:
x - y = 2
x + y = -3
The y terms:
-y and
+y → add to eliminate y.
Add them:
(x + x) + (-y + y) = 2 + (-3)
→ 2x + 0 = -1
→ 2x = -1
→ x = -1/2 or -0.5
Plug x = -1/2 into second equation:
x + y = -3
-1/2 + y = -3
y = -3 + 1/2 = -5/2 or -2.5
✔ Solution:
(-1/2, -5/2) or
(-0.5, -2.5)
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Problem 4:
Equations:
6x + 5y = 4
6x - 7y = -20
Both have
6x, so if we
subtract the second equation from the first, the x’s will cancel.
Subtract:
(6x - 6x) + (5y - (-7y)) = 4 - (-20)
→ 0 + (5y + 7y) = 4 + 20
→ 12y = 24
→ y = 2
Now plug y = 2 into first equation:
6x + 5(2) = 4
6x + 10 = 4
6x = -6
x = -1
✔ Solution:
(-1, 2)
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Problem 5:
Equations:
2x - 3y = 12
4x + 3y = 24
The y terms:
-3y and
+3y → add to eliminate y.
Add them:
(2x + 4x) + (-3y + 3y) = 12 + 24
→ 6x + 0 = 36
→ 6x = 36
→ x = 6
Plug x = 6 into first equation:
2(6) - 3y = 12
12 - 3y = 12
-3y = 0
y = 0
✔ Solution:
(6, 0)
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Final Answer:
1. (2, -3)
2. (-1, -3/2)
3. (-1/2, -5/2)
4. (-1, 2)
5. (6, 0)
Parent Tip: Review the logic above to help your child master the concept of elimination using multiplication worksheet answers.