Historical clue formulations

• It has its x's and y's — 2026-08-18
• – — 2026-08-05
• Field of unknowns — 2025-10-04
• Precursor to precalculus — 2024-07-20
• Something with an "x" factor? — 2020-01-23
• Something with many variables to consider — 2019-12-15
• Subject with variables — 2018-11-11
• Quest for the unknown? — 2015-12-13
• "Solve for x" subject — 2011-11-08
• Field with unknowns — 2011-10-02
• Field of unknowns? — 2007-06-20
• Quadratics and such — 2001-03-04
• Search for the unknown? — 1997-11-18
• Search for x — 1997-07-27
• Search for the unknown? — 1994-01-20