Are you having problems understanding the learning unit Answers to the Exercises "SN/E Competition"? Perhaps you are lacking the following basics / background:
ChemistryOrganic ChemistrySubstitution Reactions
First, this learning unit describes the mechanistic reasons for the competition of elimination and nucleophilic substitution. Then, the different parameters that influence the SN2/E2 competition as well as the SN1/E1 competition are discussed. After working through the learning unit, one should be able to predict, depending on given parameters, the predominant mechanism of a reaction or to choose the parameters of a reaction, so that a mechanism desired actually mainly occurs, respectively.