The Real Number System ($\mathbb{R}$) is explored through its fundamental subsets: Natural, Whole, and Integers. The system is categorized into Rational ($\mathbb{Q}$) and Irrational ($\mathbb{Q}’$) numbers, distinguished by their decimal representations as terminating/recurring versus non-terminating/non-recurring. The concept of set closure is defined, examining how various subsets (N, Z, R) behave under the four basic arithmetic operations (addition, subtraction, multiplication, and division) to determine operational self-sufficiency.

Examination of the fundamental economic problems faced by all societies: scarcity, choice, and opportunity cost. This analysis outlines why societies must answer the three basic economic questions regarding production and distribution.

The Law of Demand explains the inverse relationship between price and quantity demanded, subject to the *ceteris paribus* assumption. This relationship is visualized via the downward-sloping demand curve and formulated mathematically by the demand function. Demand relationships are further classified into Derived (input based on final good), Joint (complementary consumption), Competitive (substitutes), and Composite (single resource with multiple uses).

Economic demand requires both the willingness and the financial ability (purchasing power) to acquire goods, distinguishing it from mere desire or want. Effective demand drives market transactions and resource allocation.

Economics studies how societies manage scarcity and unlimited wants, leading to the necessity of choice and the establishment of economic systems (Market, Command, Mixed) to allocate resources effectively.