With this proportion :
αd:αr=180∘:π
in which αd is the measure of the angle in degree
and, αr is the measure of the angle in radians.
So, if you want to convert an angle from radians in degree:
ad=αr⋅180∘π
and if you want to convert an angle from degree to radians:
ar=αd⋅π180∘
In our case :
ad=54π⋅180∘π=225∘