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8th grade · Math · Unit 10 of 17

Equations with Brackets

Solve ax = b, x ÷ a = b, ax + b = c and a(x + b) = c

What your child practices

Solving one-variable equations, including ones with brackets and negative numbers, checking by substitution, and spotting a common mistake with the distributive property.

Maine Learning Results learning standard: 8.EE.C.7 · solving linear equations that need the distributive property

How we explain it

Children can open this short lesson before they practice.

  1. Undo brackets by dividing both sides, or by expanding.
  2. Do the same thing to both sides.
  3. Check by putting your answer back into the equation.

Example: Solve 2(x + 3) = 14. Divide both sides by 2: x + 3 = 7. Subtract 3: x = 4. Answer: x = 4

Equations with Brackets in Maine

In the Maine Learning Results, this is unit 10 of 17 in 8th grade Math, after Tables, Graphs & Linear Relations and before Congruent Shapes.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Maine Department of Education

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Solve for x: 5(x − 2) = -15

    answer box

  2. Question 2

    Solve for x: 5(x − 2) = 20

    answer box

  3. Question 3

    Dev wrote 4(x + 5) = 28 as 4x + 5 = 28. What went wrong?

    • He should have divided by x first.
    • He should have subtracted 4 from both sides.
    • He multiplied only x by 4. The 5 must be multiplied by 4 too.
    • Nothing. The two equations are equivalent.

  4. Question 4

    Which value of x makes 6x + 9 = 27 true?

    • 5
    • 2
    • 3
    • 4

  5. Question 5

    Solve for x: 3x = 6

    answer box

  6. Question 6

    Which equation is equivalent to 2(x + 7) = 35?

    • x + 14 = 35
    • 2x + 2 = 35
    • 2x + 7 = 35
    • 2x + 14 = 35

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