In any question like this, there are 8 possible answers. Of the 8, 4 are acute angles and 4 are obtuse. So any pair are either equal to each other, or they are supplementary. In this case the two given angles are equal.
We have a little bit of both in this question.
Solution
3x + 174 = - 7x + 94 Alternate exterior angles. Add 7x to both sides.