Find the missing angle of the triangle

A triangle has one interior angle that has a measure 45°, another interior angle that  has measure x°, and an exterior angle that has measure 85°, as shown in the diagram.
What is the value of x?

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The adjacent angle to 85° is equal to 95°, since angles on a straight line add up to 180°.

Therefore, the interior angles of the triangle would be:
45°, 95°, and x°

45 + 95 + x = 180   {angles of a triangle add up to 180}
140 + x = 180   {combined like terms}
x = 40°   {subtracted 140 from each side}


- Algebra House