Explanation:
yes, the other answer is correct (except for the fact that you are subtracting 37 from 180 and not the other way around).
but to add about the why :
just look at the picture. when you imagine to rotate the line (that points away from the basic, horizontal line) around the point, where both lines meet, what do you get ? a circle. its center is that point, where both lines meet.
and on each side of the basic line there is therefore a half circle. and a half circle represents 180 degrees.
that is why always all angles above or below a line around a certain point sum up to 180 degrees.