# Evaluate an algebraic example

You evaluate an algebraic expression when you try to find the value of the algebraic expression by substituting a given number for each variable.

Then you can simplify the resulting numerical expression using the order of operations.

## Examples showing how to evaluate an algebraic expression.

Example #1

Evaluate 2a - 25 ÷ b for a = 6 and b = 8

Substitute 6 for a and 8 for b

2a - 25 ÷ b = 2 x 6 - 25 ÷ 8

Simplify the power

2a - 25 ÷ b = 2 x 6 - 32 ÷ 8

Multiply and divide from left to right

2a - 25 ÷ b = 12 - 4

Subtract

2a - 25 ÷ b = 8

Example #2

Evaluate a2 - 2b + c for a = 4, b = 6 and c = 3

Substitute 4 for a, 6 for b, and 3 for c

a2 - 2b + c = 42 - 2 x 6 + 3

Simplify the power

a2 - 2b + c = 16 - 2 x 6 + 3

Perform the multiplication

a2 - 2b + c = 16 - 12 + 3

Add and subtract from left to right

a2 - 2b + c = 4 + 3

a2 - 2b + c = 7

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