Basic Algebra: Expressions and Equations
Use a letter for the unknown, find the value of an expression, solve an equation one balanced step at a time, and turn words into algebra. Always check by putting your answer back in.
What it is
Algebra is arithmetic with a placeholder. When you do not know a number yet, you write a letter for it, such as x or n. Then you can write down what you know about it and work it out.
- An expression is a math phrase with no equals sign: 3n + 5.
- An equation says two things are equal: 3n + 5 = 20.
You will do three jobs in this lesson: find the value of an expression, solve an equation, and translate words into algebra.
Why it matters on the exam
Algebra items are among the most frequent in the Numerical Ability part of the exam. You will see "find the value of ... when x = ...", "solve for x" and "a number decreased by ..." items. Almost every word problem (age, money, work, geometry) is solved by writing one equation. So algebra is the engine behind many other items.
At work, the same skill helps you rearrange a formula, check a computation, or figure out a missing amount in a report.
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