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Math · Algebraic Thinking
Solving One-Step Equations
An equation is a balanced seesaw. To find the missing number, isolate the variable using the opposite operation — and always do it to both sides.
⚖️Keep It Balanced
Both pans weigh the same → the scale is balanced. Whatever you do to one side, do to the other!
🪜Solve It Step by Step
1
Read the equation
5 is the constant stuck to x. We want x all alone.
2
Use the inverse operation
+5 undoes with −5
The opposite of adding 5 is subtracting 5.
3
Do the SAME thing to both sides
4
The variable is isolated — that's the solution!
x is alone ✓
5
Verify — plug it back in
It makes the equation true, so x = 7 is correct!
🔁Opposite (Inverse) Operations
➕➖ Add & Subtract
If a number is added, subtract it from both sides.
✖️➗ Multiply & Divide
If a number multiplies, divide both sides by it.
✏️Try These Two
Multiplication → divide
4n = 20
÷4 both sides4n ÷ 4 = 20 ÷ 4
n = 5
Check: 4 × 5 = 20 ✓
Division → multiply
y ÷ 3 = 6
×3 both sidesy ÷ 3 × 3 = 6 × 3
y = 18
Check: 18 ÷ 3 = 6 ✓
🔑Key Terms
🔤Variable A letter (like x or n) that stands for an unknown number.
🟰Equation A math sentence saying two expressions are equal.
🔁Inverse Operation An operation that "undoes" another (+ undoes −, × undoes ÷).
🎯Isolate To get the variable all alone on one side.
🧱Constant A number on its own, with no variable attached.
✅Solution The value of the variable that makes the equation true.
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Remember: whatever you do to ONE side, do the EXACT same thing to the OTHER side — then check your answer by plugging it back in!