In algebra you can use a letter to represent an unknown number.

Apuntes

• Subtopic: Basic Concepts in Algebra In algebra, a letter is used to represent an unknown number. An expression contains numbers and letters but does not include an equals sign. For example, 5n + 4 is an expression. An equation, however, includes numbers, letters, and an equals sign; for instance, 5n + 4 = 19. In the expression 5n + 4, there are two terms: 5n and 4. The term 5n is one term, and 4 is the other. The letter n is called a variable because it can take different values. The coefficient of n is 5, as it is the number multiplying the variable. • Subtopic: Components of an Equation In the equation 5n + 4 = 19, n is the unknown number to be determined. The number 5 is the coefficient of n. The numbers 4 and 19 are constants. A constant can also be represented by a letter, such as π. Pi (π) is the ratio of a circle’s circumference to its diameter and is approximately 3.14. • Subtopic: Using Variables to Solve Problems Variables help solve various problems involving unknown quantities. For example, consider a bag of sweets. If you don’t know how many sweets are inside, you can represent that unknown with a letter and set up an equation to find the answer.