This book is aimed at students who encounter mathematical models in other disciplines. It assumes some knowledge of calculus, and explains the tools and concepts for analyzing models involving sets of either algebraic or 1st order differential equations. The text emphasizes commonalities between these modelling approaches. The approach is practical, aiming at insight to understand the mathematical principles, but recognizing that real world modelling uses the computer algebra software. Hands on exploration is supported by giving software commands interspersed in the text, as well as their output.