Linear Expressions & Equations
Writing, simplifying, and evaluating algebraic expressions, and solving single-variable linear equations — excludes systems (see systems-of-equations), inequalities (see inequalities), and polynomial/radical expressions (see polynomials-quadratics, radical-rational-expressions)
Patterns & Sequences
Arithmetic and geometric sequences, pattern recognition, and nth-term formulas — classified under algebra because the core skill is generalizing a rule, even though SSAT places it under Number Concepts