"BASIC MATH. An Introduction to Calculus" is an easy way to learn mathematics. This textbook has four main chapters. The first chapter deals with set theory, the number system, and the real line with the Cartesian system of the plane and space. The second chapter shows some applications of set theory, permutations, combinations, relations, and functions. The third chapter illustrates translations and functional models with the types of functions: real, polynomial, constant, linear, quadratic, exponential, logarithmic, trigonometric, and inverse. The fourth chapter develops equations and inequalities, as well as linear or nonlinear systems of equations and inequalities. Finally, the fifth chapter concludes with solved recapitulation exercises. This work is aimed at university students of traditional academic programs or distance education in economic, administrative, social, and humanistic sciences.