Chapter 12 focuses on ordinary general annuities, covering key calculations such as future value, present value, payment amounts, number of periods, and interest rates. It differentiates between 'ordinary' and 'general' annuities based on payment timing and interest conversion periods, providing examples of payment structures and rate conversions. The chapter also includes formulas and practical examples for computing annuity values and payments using various scenarios, including mortgages and educational savings.