The angle inside near the 120 degree angle is 60 degrees because they form a straight line. Since the other angle in the triangle is a right angle 180-90-60= 30 degrees for angle 1.
The inside angle on the isosceles triangle is also 60 degrees and since it is a base angle with the angle next to angle 2 that angle is also 60 degrees. This makes a straight line with angle 2 so angle 2 is 120 degrees.
