What you’ll learn
Solve supplementary-angle problems.
Key idea
Supplementary angles have the specified sum; an algebraic label represents the whole unknown angle measure.
Supplementary sum is180; undo the angle label only after finding its full measure.
Worked example
Enter the exact value or ordered values in the format requested below.
Angles A and B are supplementary. A=168°, and B is labeled (2x+8)°. Find B's measure in degrees as a number, not x.
- Supplementary angles have sum 180°; the missing measure is 180-168=12°.
- Its label 2x+8 gives 2x+8=12, so x=(12-8)/2=2.
Answer: 12
Quick Check
Evaluate a worked attempt at solve supplementary-angle problems, identify the first invalid step, and provide the correction.
A=167°, B=(2x+1)° are supplementary. Step1 identifies that relationship. Step2 sets A+B=90° and B=-77°. Locate the first invalid step and correct B.