Answer:
m∠A = 118°
Explanation:
Given a triangle with angle measures A = (3x+13)°, B = (x -8)°, and C = x°, you want the measure of angle A.
Angle sum
The sum of the angles in a triangle is 180°:
(3x +13) +(x -8) +(x) = 180
5x +5 = 180 . . . . simplify
x +1 = 36 . . . . . divide by 5
x = 35
The measure of angle A is ...
m∠A = (3·35 +13)° = (105 +13)°
m∠A = 118°
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Additional comment
The other two angles are ...
B = 27°
C = 35°