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Answer:
y = 55°
Explanation:
You know the sum of angles in a triangle is 180°. So, ...
25° +30° +x = 180°
And, you know a linear pair of angles totals 180°:
x + y = 180°
Substituting for 180°, we have ...
25° +30° +x = x + y
Subtracting x from both sides, we get a relation that is useful to remember:
25° +30° = y
y = 55°
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This relation is usually described as ...
An exterior angle is equal to the sum of the remote interior angles.