Find the missing angle of the triangle 42° 87° x

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.

For g(x) = 5x - 3 and h(x) = [tex]\sqrt{x}[/tex], find (g · h)(4)

Which statement accurately explains whether a reflection over the y axis and a 270° counterclockwise rotation would map figure acb onto itself?