Here is the description: I am so sorry that you are struggling with your SAT math. It is a total nonsense people say about the new SAT math being easier. It is much more challenging and requires much more thorough preparation. From the unanimous vote among my colleagues—high school math teachers—it could be inferred that Khan Academy SAT preparation course suits those students who have A sometimes B in their high school math class. If you have B and sometimes C, this program is not sufficient for you, and you need much more thorough review of math concepts, beginning with arithmetic and numbers. By the way, Khan Academy has a series of brilliant tutorials by the grade. If you go to “Subjects”, choose math, and review the concepts you are still struggling with, it will definitely help you improve your performance. Concerning the problem that you’ve mentioned, there are two basic things that you need to know about solving equations. First, that a true solution is the one that makes the left side equal to the right side, and no solution occurs when a found value, after being plugged into the original equation, makes both sides unequal. In other words, you need to find such value for k that will make one side not equal to the other. Furthermore, the simplest way to find the value that make the equation untrue, is to prove that something that has been done to one side of the equation, has not been done to the other: If a=a, then a+c≠a In the problem that you’ve mentioned, after you distribute 4 on the left side, you have: 320+4n=(3k)n Two terms (4n) and (3k)n contain n, while the third term is a constant ( 320), added only to one side. What we have to assume now is that if 4n=(3k)n similar to our (a=a) then definitely 4n+320 (as in a+b) will not be equal (3k)n . Look at the similarity: b+a≠a 320+4n≠(3k)n Do you see the pattern? If only you can find such value for k that makes 4n=(3k)n as in (a=a), then you know for sure that the original equation will not work, because you’ve added to only one side of the equation 320: 4n=(3k)n 320+4n≠(3k)n So if you solve the equation 4n=(3k)n, you can find your value for k that makes the original equation untrue. In other words, if you plug this found value k=4/3 into the original equation 320+4n=(3k)n , you will have two quantities on both sides that are equal, but to one of these quantities 320 is added to make the whole equation untrue. Algebraically, it will look like this: 4(80+n)=3∙4/3 n You simplify and you will get: 320+4n=4n This is exactly our a+b≠a 320≠0 I hope you find this explanation useful. Good luck with your studies!