Answer:
60°
Step-by-step explanation:
There are a couple of ways to think about this.
a) If we rearrange the figure so both angle vertices are in the same place, then the marked angles would overlap. The amount of that overlap is ...
125° +115° -180° = 60°
That is, the smaller angle between the diagonal lines has a measure of 60°. The measure of i is 60°.
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b) If we extend the lower horizontal line to the left, as in the attached figure, we see that the external angle of the resulting triangle is an alternate interior angle that is congruent to the one marked 125°. The remote interior angles of the triangle with respect to that angle are "i" and (180° -115°) = 65°.
The exterior angle is the sum of the remote interior angles, so we have ...
125° = i + (180° -115°)
i = 125° +115° -180° = 60° . . . . as above
