Using angles of Triangle, the answer is 81.
What is Triangle?
A triangle is a closed, 2-dimensional shape with 3 sides, 3 angles, and 3 vertices. A triangle is also a polygon.
According to the question,
The sum of angles of triangle is 180⁰.
180⁰ - 99⁰ = 81⁰
Hence, the answer 81.
Learn more about Triangle here
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