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Lesson 3 of 5

SHORTCUT

Two-step equations: the balance

Undo in reverse order — constants first, coefficient last.

The question

Solve 2x + 6 = 18

The trick

Picture a balance scale. Whatever you take off one side you take off the other. Remove the loose number first, then split what's left.

Worked example

  1. 1Take 6 off both sides: 2x = 12
  2. 2Divide both sides by 2: x = 6
  3. 3Check: 2 × 6 + 6 = 18 ✓

So: x = 6

Remember it like this

Unwrapping a parcel: the tape comes off before the box opens. Undo the outermost thing first.

In the exam

Always substitute your answer back into the original equation — it takes five seconds and catches nearly every sign error. If a question is worth 3 marks, the checking line is often where the third mark lives.

Why it works

An equation is a statement that two sides weigh the same. Any operation applied to both sides keeps them equal, so the truth of the statement never changes.

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Try it yourself

0/4 correct
  • 1

    3x + 4 = 22. What is x?

  • 2

    2x − 7 = 9. What is x?

  • 3

    5x + 10 = 35. What is x?

  • 4

    4x − 3 = 17. What is x?