Answer:
145°
Explanation:
You want the exterior angle of a triangle that has remote interior angles with measures 115° and 30°.
Exterior angle
The measure of an exterior angle of a triangle is equal to the sum of the remote interior angles:
∠1 = 115° +30°
∠1 = 145°
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Additional comment
You can see how this works if you consider the unmarked angle in the triangle to be "u", then its measure satisfies two sums: one is the sum of the interior angles; the other is the sum of angles of a linear pair.
115° +30° +u = 180*
∠1 +u = 180°
Combining these equations, we have ...
∠1 +u = 115° +30° +u
If we subtract u from this equation, we have ...
∠1 = 115° +30°