# Skill variation ladder
Skill: [prealg.algebraic-thinking.word-to-expression](/math/skills/prealg/algebraic-thinking-word-to-expression)
Family: Equations, Variables, Expressions, and Inequalities
Difficulty grows by changing representation, numeric range, constraint count, distractors, language load, and transfer context while keeping the presentation mobile-legible.
## Variations
- 6. Advanced enrichment: Reason about the general method or a non-routine variant.
- 5. Challenge extension: Combine the skill with a second idea, hidden constraint, or explanation requirement.
- 3. Core task: Solve the target skill independently.
- 1. Foundation recognition: Notice the relevant quantity, shape, relation, or constraint before calculating.
- 2. Guided strategy: Use a visible scaffold, model, or narrowing move to choose a valid next step.
- 4. Transfer form: Apply the same idea when numbers, wording, or representation changes.
## Method
Ask a concrete task question before making school-standard claims.
Use a given representation once the surface contract is bound.
Validate the learner state through the bound format; wrong, correct, hint, and reveal states must remain distinguishable.