(a) The angles of a quadrilateral are xº, 2xº, 4xº, 5xº. Find x.
(b) The angles of a triangle are 2xº, 5xº, (x+20)º. Find x.
x°+2x°+4x°+5x°=12x°
360x° : 12x° = 30
x = 30
2x°+5x°+x°+20°=180° | -20°
8x°=160°
160x° : 8x° = 20
x = 20
