Answer:
d = 140°
Step-by-step explanation:
the sum of the interior angles of a polygon is
sum = 180° (n - 2) ← n is the number of sides
a nonagon has 9 sides , then
sum = 180° × 7 = 1260°
sum the angles and equate to 1260
150° + 130° + 130° + 150° + 140° + 140° + 150° + 130° + d = 1260°, that is
1120° + d = 1260° ( subtract 1120° from both sides )
d = 140°
