THE SHORT VERSION

Keep both sides balanced and check your answer.

WHY CARE?This is here to help you understand the idea and use it—not merely finish a page.WHAT NEXT?Read the first section, explain it in your own words, then try the small task below.
OPEN ONLY WHAT YOU NEED.Start with the short answer. Expand each idea for examples, mistakes and the fuller explanation. Slides or video are added when they genuinely make the subject clearer.
01 · THE BIG IDEA

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IN PLAIN ENGLISH

An equation says two expressions have the same value. To keep that equality true, perform the same valid operation on both sides. Your goal is to leave the unknown on its own.

02 · EXAMPLE

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IN PLAIN ENGLISH

Start with 3x + 5 = 20. Subtract 5 from both sides: 3x = 15. Divide both sides by 3: x = 5. Check in the original equation: 3 × 5 + 5 = 20.

03 · TRY IT

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IN PLAIN ENGLISH

For 2x + 4 = 18, what is x?