A real lesson from Pre-Algebra · Unit 6, Lesson 3 · free

Solving two-step equations

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Learn it

An equation like 2x + 3 = 11 is a scale that balances. Whatever you do to one side, you must do to the other — that’s the whole game.

“Two-step” means exactly two moves undo everything that’s been done to x. Undo them in reverse order — like taking off shoes before socks:

Move 1: undo the adding or subtracting.
Move 2: undo the multiplying or dividing.

— in a full course, this button never runs out.

Watch one

2x + 3 = 11

2x + 3 − 3 = 11 − 3undo the +3 first

2x = 8

2x ÷ 2 = 8 ÷ 2then undo the ×2

x = 4

Check it (always, it takes five seconds): 2(4) + 3 = 8 + 3 = 11 ✓

Try one, with the assistant

3x − 4 = 17

Step 1 — which move first?

Now alone

5x + 2 = 27

Solve it on paper, then choose:

Mastery check — no hints from here

Two questions, unaided — exactly how real course assessment works. (In a full course this feeds the grade book.)

1.  Solve:  4x − 9 = 19

2.  Solve:  x⁄3 + 5 = 9