courses › Pre-Algebra

Substitute values, tidy expressions, and undo one operation.

In your head, jot if needed · no calculator why?

Learn first (about 3 minutes)

Opens at level 15.

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Builds on: Order of operations (not open yet)

skills · practice stats

From rounds of this course only: box, review and trial answers are left out. Once a skill has 40 tries, it compares your first 20 tries with your last 20.

• One-step equations par 6 s not tried yet

  worked example

  6x = 66. What is x?

  Answer: 11

  1. Undo × 6 by dividing both sides by 6: x = 66 ÷ 6 = 11.

• Evaluate an expression par 11 s not tried yet

  worked example

  Evaluate −9x² − 5x − 5 when x = 3.

  Answer: -101

  1. x² = 3² = 9.
  2. −9x² = −9 × 9 = −81 and −5x = −5 × 3 = −15.
  3. Add: −81 − 15 − 5 = −101.

• Combine like terms par 12 s not tried yet

  worked example

  Simplify 6(x + 6) + 2x + 7. What is the coefficient of x?

  Answer: 8

  1. Distribute: 6(x + 6) = 6x + 36.
  2. Collect: 6x + 2x = 8x and 36 + 7 = 43, so it is 8x + 43.
  3. The coefficient of x is 8.

rest ladder

Win 3 of your last 4 rounds and the course rests. A win is 90% right, within 2× the round's par. Pass the review when it comes back and the next rest is longer.

1. 1 day
2. 3 days
3. 7 days
4. 14 days
5. 30 days
6. 60 days
7. mastered · every 90 days

your rounds

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