There are two lines that are marked with a perpendicular line, and that indicates that the two lines have the same length (i.e., the triangle is isosceles, and so the angle on the upper right (between the second and third line protruding from the top point) is 30 deg. The value of the largest angle at the top (from the first line to the third line) is 60 deg because the large triangle has angles of degree measure 90 and 30, and they sum to 180 so x+90+30=180->x=60. The angle marked by x should be 60-30=30 deg
