The Venn diagram helps to solve this type of problem. Here's the key:
A=Commerce students who didn't take any of the 3 subjects.
B=Ins only students
Now some figures:
So, E=8, F=4, G=8.
(a) A=2 students took none of the 3
(b) C=70 students took math only
(c) E=8 students took ins and eng only
(d) B+C+D=80 students took only one course
(e) E+F+G=20 students took only two courses