Step-by-step explanation:
You want the external angle to be 45°.
If n = number of sides, the external angles are each 360°/n = 45°
n = 360/45 = 8
The shape is a regular octagon.
u = -3
Step-by-step explanation:
12 - 2u = 9u + 45
12 - 2u + 2u = 9u + 2u + 45
12 = 11u + 45
12 - 45 = 11u + 45 - 45
-33 = 11u
-33/11 = u
-3 = u
Check:
12 - 2(-3) = 9(-3) + 45
12 + 6 = -27 + 45 = 18