Answer
50°, 60° and 70°
Work Step by Step
1. Internal angles of a triangle have a sum of 180°
(x+20)+(210-3x)+(x)= 180
2. Solve the equation for x
x-3x+x=180-210-20
-x=-50
x=50$^{\circ}$
3. Then find other two angles by replacing x=50
(50)+20= 70$^{\circ}$
210-3(50)=60$^{\circ}$
