The formula for the sum of all the angles of a polygon with n sides is
(n - 2)*180. e.g. for a triangle, n = 3, and sum of angles = (3 - 2)*180 = 180.
For a pentagon, n = 5, so sum of the 5 angles = (5 - 2)*180 = 540 degrees.
You already know the 4 angles. Add them up and subtract the total from 540 to get
the measure of the 5th angle, which is your answer :)