Answer:
yes you are right
The side of a cube when the diagonal is known is found using the formula:
Side = √3 * diagonal/3
Replace diagonal with 20:
Side = √3 * 20/3
Side = √3 * 6 2/3
Side = 11.547 cm (Round the answer as needed).
angle ABE = 115.5
angle DBE = 25.5