More detail on the problem is needed but in general the degree of rotational symmetry means the number of degrees you have to rotate an object until it looks no different to the original position. For example for a square it is 90 degrees. For a Pentagon it is 360/5 = 72 degrees. If an object has to be turned all the way around it is 360 (i.e. it doesn't really have rotational symmetry. For a circle the degree of rotational symmetry is not defined (i.e. it is infinitely small). You may find the book "What Can I Do to Help My Child with Math When I Don't Know Any Myself?" (ISBN 9780974168906) helpful.