Virginia SOL Math / Algebra I / Expressions & Operations

A.EO.1

Expressions & Evaluating

What you'll learn

  • Translate verbal situations into algebraic expressions
  • Evaluate expressions for given values of the variables
  • Use the order of operations to simplify expressions

Words to know

Variable —
a letter that stands for an unknown number
Expression —
numbers and variables combined with operations, no equals sign
Coefficient —
the number multiplied by a variable, like the 3 in 3x
Term —
a single number, variable, or product, separated by + or -
Evaluate —
replace each variable with a value and simplify
Substitute —
put a given value in place of a variable

Why it matters Algebraic expressions let us describe a rule once and reuse it for any value, from a phone plan's monthly cost to the perimeter of any rectangle.

Worked examples

Model ItI do

Evaluate 3x + 5 when x = 4.

Substitute 4 for x: 3(4) + 5. Multiply first, then add: 12 + 5 = 17.

Try It TogetherWe do

A taxi charges $2 to start plus $3 per mile. Write an expression for the cost of m miles, then find the cost of 6 miles.

Cost = 2 + 3m. For 6 miles: 2 + 3(6) = 2 + 18 = 20, so the ride costs $20.

Now YouYou do

Evaluate 2a^2 - 7 when a = 3.

Substitute 3 for a and follow the order of operations. Check your answer in the back of this chapter.

Practice

Mastered 0 of 11

Warm-up

Ease in with the basics.

  1. 1.Evaluate x + 7 when x = 5.

  2. 2.Name the coefficient in the term 6x.

  3. 3.Evaluate 4x when x = 3.

On Level

The core Quick Check from the book.

  1. 1.Evaluate 5x - 2 when x = 6.

  2. 2.Write an expression for '8 less than twice a number n'.

  3. 3.Evaluate a + b^2 when a = 4 and b = 5.

  4. 4.Name the coefficient in the term -7y.

  5. 5.Evaluate (10 - x) / 2 when x = 4.

Challenge

Stretch your thinking.

  1. 1.Evaluate 2a^2 - 3b when a = 3 and b = 4.

  2. 2.Write an expression for 'the quotient of 5 more than a number n and 2'.

  3. 3.Evaluate (2x + 6) / (x - 1) when x = 4.