Author note — to cover

Solve linear pairs by substituting an expression for one unknown taken from the equation where its coefficient is already 1, e.g. y = 2x + 1 into 3x + 2y = 16, expanding brackets carefully. This is the method the Higher linear-quadratic page depends on. Both tiers. (A19)

• Fluency — direct questions on simultaneous equations by substitution, limited to this lesson's stated scope (4 questions).
• Application — use the same skill in unfamiliar or contextual questions without introducing a later method (4 questions).
• Check — questions built around the exclusions and likely misconceptions named in the lesson brief (4 questions).