Author note — to cover

Set up equations from angle sums in triangles and on straight lines, equal sides of named shapes, and perimeters and areas with algebraic lengths; solve, then give the angle or length asked for, not the x. The angle facts and mensuration formulae themselves live on the Geometry strand. Both tiers. (A21)

• Fluency — direct questions on equations from angles and perimeters, 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).