Describing Triangles

The interior angles theorem tells us that the sum of angles in a triangle is always $180^\circ.$ Using this we can find the measure of the unknown interior angle, which we can denote $x,$ in the triangle. $x+65+57=180 \; \Leftrightarrow \; x=180-65-57=58$ Thus, the measure of the unknown interior angle is $58^\circ.$ Together with $v,$ a straight angle is formed.

That means the sum of them is $180^\circ$ $m\angle v+58^\circ=180^\circ \quad \Leftrightarrow \quad m \angle v=122^\circ$ We have found the measure of $\angle v$ and it is $122^\circ.$