Virginia SOL Math / Grade 5 / Patterns, Functions & Algebra

5.PFA.2

Variables and One-Step Equations

What you'll learn

  • Use a variable to stand for an unknown quantity
  • Write a one-step equation from a situation
  • Solve one-step equations using inverse operations

Words to know

Variable —
a letter or symbol standing for an unknown number
Equation —
a math sentence showing two amounts are equal
Inverse operation —
an operation that undoes another
Solve —
find the value that makes an equation true
Expression —
numbers and variables combined with operations

Why it matters Variables let us write and solve equations for unknowns, a key tool for solving real problems in math and science.

Worked examples

Model ItI do

Solve x + 7 = 12.

Undo the addition by subtracting 7 from both sides. That gives x = 12 - 7, so x = 5.

Try It TogetherWe do

Write and solve an equation: a number times 4 is 20.

Let n be the number, so the equation is 4n = 20. Divide both sides by 4 to get n = 5.

Now YouYou do

Solve y - 3 = 9.

Use the inverse operation to undo the subtraction. Check your answer in the back of this chapter.

Practice

Mastered 0 of 11

Warm-up

Ease in with the basics.

  1. 1.Solve x + 2 = 6.

  2. 2.Solve 2n = 10.

  3. 3.Solve y - 1 = 7.

On Level

The core Quick Check from the book.

  1. 1.Solve x + 5 = 11.

  2. 2.Solve 3n = 18.

  3. 3.Solve y - 4 = 10.

  4. 4.Write an equation: a number plus 6 equals 15.

  5. 5.Solve m divided by 2 = 8.

Challenge

Stretch your thinking.

  1. 1.Solve 7x = 84.

  2. 2.Write and solve an equation: 6 less than a number is 19.

  3. 3.Solve m divided by 4 = 12.