Final answer:
The third section of the Liber Abaci describes Indian mathematics, including the use of decimals, the number zero, and negative numbers.
Step-by-step explanation:
The third section of the Liber Abaci describes Indian mathematics. Indian mathematicians made significant contributions to the field of mathematics, including the use of decimals, the number zero, and negative numbers. They also developed trigonometric functions and calculated the value of pi with a high degree of precision. The Liber Abaci was written by Leonardo of Pisa and introduced the Hindu-Arabic numeral system to Europe in the 13th century.