"The study of mathematics, like the Nile, begins in minuteness but ends in magnificence". The aim of this book is to give the reader an opportunity to learn and to know interesting results in the elementary theory of numbers. A reasonably large number of problems on solving systems of equations have been provided to enable the students to deepen their understanding of the subject. This book is aimed at students, researchers and anyone with an interest in numbers and equations. Some aptitude is needed for general readers. It will be particularly useful to students who wish to do research in polynomial Diophantine equations. The author's goal is to illustrate the art of finding integer solutions to systems of Diophantine equations. We hope the students may be motivated to search for integer solutions to systems of multi degree multivariate polynomial Diophantine equations.