To clockmaster: the angle of an hour is 30 degrees (12 hours make 360 degrees), not 15 degrees.

hour hand moved 1/3 of 30 degree, 2/3 is left therefore, 2/3*30 degree=20 degree

5 degrees. By the time minute hand moved from 0 to 20 min, hour hand passed 1/3 of distance from 4 to 5 hours, which is 1/3 of 15 degrees, which is 5 degrees.