Watch as Kaplan GRE expert Adi Hanash walks you through a GRE Problem Solving question that asks you to solve a system of linear equations. Review how to use substitution in GRE Algebra. Remember that knowing strategy, such as substitution and combination, is important for success on the GRE. You also want to be familiar with how the GRE will be testing you on these types of problems. For more tips on how to ace the test, visit our Kaplan Grad Prep blog at http://blog.kaplangradprep.com/.