Skip to lesson

Math · Grade 8 Math

Chapter 4: Linear Equations in One Variable

Equations with Brackets and Fractions

Clear the clutter first.

Lesson
3
Time
About 19 minutes
0 of 7 done

Step 1: Let's Learn

Read it, or press Listen and follow the words.

Expand any brackets before collecting terms. 3(x + 2) = 18 becomes 3x + 6 = 18.

Fractions can be cleared

Multiply every term by the denominator. x/4 + 2 = 5 becomes x + 8 = 20.

Every term, both sides

Multiplying only some terms changes the equation. The 2 has to be multiplied as well as the x/4.

Then it is an ordinary equation

Once brackets and fractions are gone, collect the x terms on one side and solve.

Multiply through to clear fractions

For x/3 + 1/2 = 2, multiply every term by 6, the least common denominator: 2x + 3 = 12. Clearing fractions at the start turns a messy equation into a clean one, and it costs one extra step.

Every term, without exception

The multiplier must be applied to every term on both sides, including any that are already whole numbers. Missing one term is the standard error here, and it produces an equation that is no longer equivalent.

Expand brackets before gathering

Deal with brackets first, then clear fractions, then gather like terms, then solve. Following a fixed order means you are never deciding what to do next, which is where hesitation turns into mistakes.

Check against the original equation

Substitute into the equation as first given, fractions and all. Checking against your cleaned-up version would miss an error made in the clearing step, which is exactly the step most likely to go wrong.

Step 2: Try It Yourself

The bracket drawn as a rectangle, cut into the two products it makes.

The multiplier reaches every term inside the bracket.

6 + 6 + 6 = 18

3 × 6 = 18

3 × 6 = (3 × 2) + (3 × 4) = 6 + 12 = 18

The array is cut into 3 × 2 and 3 × 4. Two easier facts that add to the same total.

Step 3: Watch an Example

One step at a time.

Watch Ana Clear a Fraction

Ana solves x/3 + 4 = 10.

  1. Step 1

    She multiplies every term by 3, including the 4 and the 10.

Step 4: Your Turn

Practice makes it stick.

The Bracket

Problem 1 of 2

4(x + 3) = 32. What is x?

The Fraction

Problem 2 of 2

x/2 + 3 = 9. What is x?

Clear and Solve

1 of 4

2(x + 5) = 24. What is x?

2 of 4

x/5 = 4. What is x?

3 of 4

3(x − 2) = 15. What is x?

4 of 4

x/4 + 1 = 6. What is x?

Step 5: Quick Check

Show what you know.

Question 1 of 1

5(x + 1) = 40. What is x?

What You Learned

  • Expand brackets and clear fractions before collecting terms.
  • Multiply every term on both sides, not only the fractional one.
  • What is left is an ordinary linear equation.