Final answer:
The primary governing philosophies of Presidents Harding, Coolidge, and Hoover were laissez-faire economic policies.
Step-by-step explanation:
The primary governing philosophy of Presidents Warren G. Harding, Calvin Coolidge, and Herbert Hoover during their respective terms in office was laissez-faire economic policies. They believed in limited government intervention in the economy and supported the idea of rugged individualism, where individuals were responsible for their own success or failure. While Herbert Hoover's policies expanded public works programs and created the Reconstruction Finance Corporation to stimulate the economy during the Great Depression, his overall philosophy aligned with the idea of limited government intervention.