D/3 w1.

The image contains mathematical problems written on a blackboard. The first problem involves two circles with centers O1 and O2, and radii r1=20cm and O02=27cm. The task is to find r2.

The second problem shows a circle with points A, B, and C on its circumference. An angle of 135 degrees is indicated. Another circle has points A, B, and C on its circumference, with an angle of 74 degrees indicated at vertex B.

The image also contains some formulas at the top left, which are partially visible.