The question says to find the measure of the angle. But I am not sure how to solve it.

Given the angle in the diagram to be 50 degrees, to get the rest of the angle. we will subtract the given angle ffrm 360 since sum of angles in all the quadrants is 360.
Let x be the unknown angle, hence;
x + 50 = 360
x = 360 - 50
x = 310 degrees
Hence the measure of the angle is 310 degrees