Given data:
The given biology percentage is B=40%.
The given chemistry percentage is C=24%.
The percenage of earth science as compare to physics is E=P+4%.
The expresion for the sum of all subjects is,
B+C+E+P=100%
40%+24%+E+P=100%
E+P=36%.............................(I)
Substitute given value in the above expression.
P+4%+P=36%
2P=32%
P=16%
The nummber of students assigned earth science is,
E=16%+4%
=20%
Thus, the percentage of the students assigned to the physics subject is 16%.