Before you start yelling at the dinner table, master the two-step habit: move the loose number with the inverse operation, then do the opposite to the number attached to x. Whatever you do to one side, you MUST do to the other. Then plug your answer back in and prove it.
The 3 Rules
1
Isolate the variable
Get it on a side by itself.
2
Use the inverse operation
If you want to move something to the other side, do the inverse operation (the opposite operation. example: + is the opposite of −).
3
Whatever you do to one side, you MUST do to the other.
Equation1 of 32
3x+ 5=20
Step 1: Targeting
What do we get rid of first?
OR
Isolating Variables: One- and Two-Step Equations: a guide for parents
Grades 6–8 • Math • Free, no login
Get x alone: undo the loose number first, then the multiplier, keeping both sides balanced.
Kitchen Table Prompt
Ask what is attached to x. Move the loose number first with the inverse operation, then do the opposite to the number attached to x. Whatever you do to one side, you MUST do to the other. Finish by plugging the answer back in to prove it.
Standards this lesson covers
Common Core: 6.EE.B.5, 6.EE.B.7 & 7.EE.B.4 (Reason About and Solve One-Variable Equations; Use Variables to Represent Quantities and Solve Multi-Step Real-World Problems)
Texas (TEKS): TEKS 6.10A & 7.11A (Model and Solve One- and Two-Step Equations Using Concrete and Pictorial Models, Inverse Operations, and Properties of Operations)
Florida (NGSSS): B.E.S.T. MA.6.AR.2.1 & MA.7.AR.2.2 (Write and Solve One-Step and Two-Step Linear Equations in One Variable Using Inverse Operations)
Virginia (SOL): 6.13 & 7.12 (Solve One- and Two-Step Linear Equations in One Variable Using Inverse Operations and Maintain Equality)
North Carolina (SCOS): NC SCOS 6.EE.7 & 7.EE.4 (Apply Properties of Operations to Solve Numerical and Algebraic Equations by Isolating the Variable)
