Find D

A + B + C = 180°

2x + 0.5x + 2x = 180°

2x + 0.5x + 2x = 4.5x

D = (A + B + C) - C

D = 4.5x - 2x = 2.5x

180°/4.5 = 40° = x

40° x 2.5 = D = 100°.

The sum of the interior angles of a triangle is $180^\circ$ . So we have

$2x+2x+0.5x=180$ $\implies$ $4.5x=180$ $\implies$ $x=40$

The angles are

$A=2x=2(40)=80^\circ$

$B=0.5x=0.5(40)=20^\circ$

$C=2x=80^\circ$

So $D$ is $\dfrac{360-80-80}{2}=$ $\color{#D61F06}\boxed{100^\circ}$