x = 57°
By using the straight line degrees(180°) and inner three triangles adding (180°) theories .
39°+90°+y = 180°(inner three triangles theory)
Therefore y = 51°
y+51°+z = 180° ( straight line theory)
When y = 51° ,
51°+51°+z = 180°
Therefore z = 78°
Finally , z +45°+x = 180° (inner three triangles theory)
As we get z = 78° in above ,
78°+45°+x = 180°
Therefore x = 57°
