Two parallel lines are cut by a transversal. One of the angles formed measures 65°. What is the measure of the co-interior (same-side…

Co-interior (same-side interior) angles lie between the two parallel lines on the same side of the transversal. When the lines are parallel, they are supplementary, meaning they add to $180°$. So the angle is $180° - 65° = 115°$, choice D. Choice A (65°) is the measure of the alternate interior or corresponding angle, which is equal, not supplementary. Choice B (25°) is the complement, $90° - 65°$, which applies to right angles and not to straight lines. Choice C (155°) comes from the arithmetic slip $180 - 25$. Equal angles pair with alternate or corresponding positions; co-interior angles add to $180°$.