Explanation:
due to the principle of identical angles in parallel lines when intercepted by an inclined line,
y = 49°
the angles above an intersected line are the same as below that intersected line (just mirrored left-right).
and at the bottom, the angles an insecticide line has with one line must be the same as with another line that is parallel to the first line.
so, both indicated angles are the same as the original angle on the top : 49°