180 - 86 = 94° (angles on a straight line add up to 180°)
180 - 123 = 57° (angles on a straight line add up to 180°)
94 + 57 = 151° ( sum of opposite interior angles of a triangle is equal to exterior angle of the other)
OR
97 + 54 = 151
180 - 151 = 29° (angles in a triangle add to 180°)
190 - 129 = 151° (angles on a straight line add to 180°)
Hope that helps!
Brainliest would he appreciated!