Wikipedia defines a mnemonic, or mnemonic device, as "any learning technique that aids memory. To improve long term memory, mnemonic systems are used to make memorization easier."
Algebra is a subject with many rules, which can be challenging and frustrating to memorize. Anything that can help make this part of learning easier should be used whenever possible. There are no magic tricks, or silver bullets that will make every subject fun to learn, but algebra seems to give many students a particularly difficult time and is the source of much frustration and angst.
Let's take a look at a simple...