Let s represent the smallest angle. Then the 3 angles are
Since it is a triangle, the sum of these angles is 180°
... s + 3s + (s+20°) = 180°
... 5s = 160° . . . . . . . . . . . . . collect terms, subtract 20°
... s = 32° . . . . . . . . . . . . . . . divide by 5
Then the 3 angles are
The largest angle is 96°.