Answer
See below.
Work Step by Step
If $a,b,c$ are the angles of the triangles and $a$ is the smallest, then: $b=a+20^\circ$, $c=2a$. We also know that $a+b+c=180^\circ$.
Thus $a+a+20^\circ+2a=180^\circ\\4a+20^\circ=180^\circ\\40=160^\circ\\a=40^\circ$
Thus the angles are: $a=40^\circ$, $b=40^\circ+20^\circ=60^\circ$, $c=2\cdot40^\circ=80^\circ$
