These two types of problems always involve two letters (usually x and y) and usually start the same way: if the problem has the words "varies directly" in it (or says two things are "proportional"), you just write down "y=kx" and start plug-and-chugging. If the problem says "varies inversely" (or variables are "inversely proportional"), you write down y=k/x and start plug-and-chugging. Sound too easy? What can I say: the same four steps will get you through every one of these things.
Basic Matrix Operations
This video covers the most basic things you can do to matrices which are the same size: adding and subtracting them. We'll also learn how to multiply them by a scalar, which is another word for constant.
One Step Unit Conversion Problems
This video demonstrates a ton of basic unit conversion problems -- kilograms to grams, meters to millimeters, years to days -- as well as some funky word problems. What all these problems have in common is that only one conversion factor is needed to get the answer.
Simplifying Roots & Radicals
This video starts things off on the right foot with square roots, demonstrating the easiest and hardest-to-mess-up method for simplifying radicals, which is where we try and get the smallest number under the root as possible.
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)