In this chapter we will apply Adominan decomposition method, the variational iteration method, and other numerical methods to handle linear and nonlinear differential equations numerically. Because the decomposition method and the variational iteration method provide a rapidly convergent series and approximations and faster than existing numerical techniques, it is therefore the two methods are considered efficient, reliable and easy to use from a computational viewpoint. It is to be noted that few terms or few approximations are usually needed to supply a reliable result much closer to the exact value. The overall error can be significantly decreased by computing additional terms of the decomposition series or additional approximations.