Answer:
? = 31°
Step-by-step explanation:
the sum of the 3 angles in a triangle = 180°
the sum of the angles in a straight angle = 180°
The lower triangle's third angle can be found as
180° - (20 + 35)° ← angle sum in triangle
= 180° - 55° = 125°
the upper triangle has angle = 125° ( vertically opposite angles ) and
180° - 156° = 24° ( straight angle ), hence
? = 180° - (125 + 24)° ← angle sum in triangle
? = 180° - 149° = 31°
