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ISEE Middle Level Mathematics Achievement · Question of the Day

ISEE Middle Level Mathematics Achievement Question of the Day

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Monday, September 7, 2026

The measure of an angle is 18 degrees more than one-third the measure of its supplementary angle. If x is the measure of the angle, which equation correctly represents this relationship?

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Question of the Day

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The measure of an angle is 18 degrees more than one-third the measure of its supplementary angle. If x is the measure of the angle, which equation correctly represents this relationship?

  1. x = (1/3)(90 - x) + 18
  2. x + (1/3)x + 18 = 180
  3. x = 3(180 - x) + 18
  4. x = (1/3)(180 - x) + 18 (correct answer)

Explanation: Let the angle be x. Its supplement is 180 - x. 'One-third the measure of its supplement' is (1/3)(180 - x). '18 degrees more than' this quantity is (1/3)(180 - x) + 18. Since this is equal to the measure of the angle x, the equation is x = (1/3)(180 - x) + 18.