Non-linear algebraic equations arising out of pipe network problems with pumps are normally difficult to solve and hence avoided by the teachers and students for a possible solution. But now these problems can be taught with interest and can be solved within a very short time in the class by using EES. In fact any kind of complex algebraic or differential equations can be solved easily, following the book, whether they arise out of a network problem or from thermodynamics or chemical engineering. Solution of ordinary and partial differential equations can be done quickly in a class either by following the finite difference method or the shooting method using the Brents's optimization tool. Application of partial and ordinary differential equations to solve real life problems are shown in plenty in the book and the reader is expected to gain plenty of confidence by solving these problems as illustrated in the book.