Most of you are probably familiar with the basic rules for solving linear equations or systems of linear equations, yet many GMAT takers fall prey to booby traps planted in these kinds of Data Sufficiency questions. In order to avoid such mistakes, you should learn well the general methods for solving Systems of Equations and become acquainted with the special cases that may appear on your test.
A set of equations to be solved simultaneously is called a System of Equations. The general rule is that a linear system with n variables usually needs n independent equations to solve it. However, the GMAT Maths questions sometimes uses special cases—offering dependent equations or asking for the value of an expression—that make things a bit more complicated. Let’s examine these more closely.