The intersection of the two red rays forms a set of vertical angle pairs. In such a pair, angles opposite one another have the same measure, so the angle opposite the one labeled 93 degrees also has measure 93 degrees.
The red ray on the right together with the black ray pointing directly to the right form a pair of supplementary angles, whose measures add up to 180 degrees. This means the angle adjacent to the one labeled 128 degrees has measure 180 - 128 degrees.
In any triangle, the interior angles' measures add up to 180 degrees. So we have
? + 93 + (180 - 128) = 180
? + 93 - 128 = 0
? = 128 - 93
? = 35
