x = 11 and vertex = 132°
the base angles of an isosceles triangle are equal, thus
4x - 20 = 2x + 2 ( subtract 2x from both sides )
2x - 20 = 2 ( add 20 to both sides )
2x = 22 ⇒ x = 11
base angles = ( 2 × 11) + 2 = 24°
vertex angle = 180° - ( 2 × 24 ) = 132°
