Algebraic Expression for "5 decreased by a number"

To find the algebraic expression for "5 decreased by a number," we need to understand what the phrase means and convert it into mathematical language.

Understanding the Phrase
"5 decreased by a number" implies that we start with the number 5 and then subtract another number from it. The phrase does not specify the second number, so we will represent it as a variable.

Representing the Unknown Number
Let's use the variable "x" to represent the unknown number that we are subtracting from 5. Using this variable, the algebraic expression for "5 decreased by a number" can be written as:

5 - x

In this expression, the number 5 is the starting point, and the variable "x" represents the number we are subtracting from 5.

Explanation of the Algebraic Expression
The expression "5 - x" means that we are subtracting the value of "x" from 5. Here's a breakdown of what each part of the expression represents:

- The number 5: This is the starting point or the base value.
- The minus sign (-): This indicates subtraction.
- The variable "x": This represents the unknown number that we are subtracting from 5.

Example Using the Algebraic Expression
Let's say we want to find the value of "5 decreased by a number" when the unknown number is 3. We can substitute the value of "x" with 3 in the expression:

5 - 3 = 2

Therefore, when the unknown number is 3, the value of "5 decreased by a number" is 2.

Conclusion
The algebraic expression for "5 decreased by a number" is 5 - x, where the variable "x" represents the unknown number being subtracted from 5. By understanding the meaning of the phrase and using the appropriate mathematical symbols, we can represent and evaluate expressions that involve subtraction.