Brainiest is my answer is correct check it first

Yes, the suggested answer is correct. 
It is possible to verify: 34*33+21=1143

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .