Question 462755
An algebraic expression is a number, variable or combination of the two connected by some mathematical operation like addition, subtraction, multiplication, division, exponents, and/or roots. 

You evaluate an expression by replacing the variable with the given number and performing the indicated operation.
When you are asked to find the value of an expression, that means you are looking for the result that you get when you evaluate the expression.

So keep in mind that vary means to change - a variable allows an expression to take on different values, depending on the situation. 


your situation you could model with the expression {{{x + 25}}} could be:

The {{{sum}}} of a number and {{{25}}}, where

*"{{{sum}}}" = +
*"a {{{number}}}" = variable {{{x}}}

or

Charles is 25 years older than Buddy. If x = Buddy's age, write an expression for Charles' age.

Since {{{x}}} represents Buddy's age, and Charles is 25 years older than Buddy, then Charles' age can be represented as {{{x + 25}}}