Explanation:
Lets third angle be x
or,10°+x+80°=180° ( sum of triangle )
or,90°+x=180°
or,x=180°-90°
or,x=90°
Answer:
90°
All angles inside a triangle add up to 180 so:
180 - 10 - 80 = 90
Therefore, the 3rd angle is 90°
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