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Math Grade 6-8 Answer Key

Solving One-Step Equations

Use inverse operations to find the unknown

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Solving One-Step Equations

Use inverse operations to find the unknown

Math - Grade 6-8

Instructions: Read each equation carefully. Use an inverse operation to isolate the variable. Show your work in the space provided.
  1. 1

    Solve for x: x + 7 = 19

    Undo adding 7 by subtracting 7.

    Subtract 7 from both sides to get x = 12. The solution is x = 12.
  2. 2

    Solve for y: y - 5 = 14

    Add 5 to both sides to get y = 19. The solution is y = 19.
  3. 3

    Solve for n: 4n = 36

    The variable is being multiplied by 4.

    Divide both sides by 4 to get n = 9. The solution is n = 9.
  4. 4

    Solve for a: a/6 = 8

    Undo division by 6 using multiplication by 6.

    Multiply both sides by 6 to get a = 48. The solution is a = 48.
  5. 5

    Solve for m: m + (-3) = 11

    Add 3 to both sides to get m = 14. The solution is m = 14.
  6. 6

    Solve for p: p - 12 = -4

    Add 12 to both sides to get p = 8. The solution is p = 8.
  7. 7

    Solve for k: -5k = 45

    A positive divided by a negative gives a negative.

    Divide both sides by -5 to get k = -9. The solution is k = -9.
  8. 8

    Solve for r: r/(-7) = 3

    Multiply both sides by -7 to get r = -21. The solution is r = -21.
  9. 9

    Solve for c: c + 2.5 = 9

    Line up the decimal points when subtracting.

    Subtract 2.5 from both sides to get c = 6.5. The solution is c = 6.5.
  10. 10

    Solve for t: t - 3/4 = 2

    Write 2 as 2/1 or think of adding three fourths to 2 wholes.

    Add 3/4 to both sides to get t = 2 3/4, which is also 11/4. The solution is t = 2 3/4.
  11. 11

    Solve for x: x/5 = -6

    Multiply both sides by 5 to get x = -30. The solution is x = -30.
  12. 12

    Solve for d: 0.2d = 4

    Since 0.2 is one fifth, 0.2d means one fifth of d.

    Divide both sides by 0.2 to get d = 20. The solution is d = 20.
  13. 13

    Solve for q: -q = 17

    Multiply or divide both sides by -1 to get q = -17. The solution is q = -17.
  14. 14

    Solve for g: g + 1/6 = 5/6

    Subtract 1/6 from both sides to get g = 4/6. Simplifying 4/6 gives g = 2/3. The solution is g = 2/3.
  15. 15

    A movie ticket costs $6. After buying the ticket, Maya has $18 left. Write and solve a one-step equation to find how much money Maya had before buying the ticket.

    Start with the money she had, subtract the ticket cost, and set that equal to the money left.

    Let m be the amount of money Maya had before buying the ticket. The equation is m - 6 = 18. Add 6 to both sides to get m = 24, so Maya had $24.
LivePhysics™.com Math - Grade 6-8 - Answer Key

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