how to construct 7and a half degree

Note: Construction of angle bisectors is a part of syllabus of class IX CBSE.
Constructing an angle measuring 7.5^o has following steps:
Construct an angle of ABC 60^o.
Construct the angle bisector PB of angle ABC such that angle PBC = 30^o.
Construct the angle bisector QB of angle PBC such that angle QBC = 15^o.
Construct the angle bisector RB of angle QBC such that angle RBC = 7.5^o.