This is a quadrilateral.....the sum of its interior angles = 360°
So
x + 2x + 108 + 108 = 360
3x +216 = 360 subtract 216 from both sides
3x =144 divide both sides by 3
x = 48
Not sides.....the sum of the interior angles.....
To see this
A square is a quadrilateral
Each interior angle = 90
So....the sum of the interior angles = 4(90) = 360 !!!!