Answer:
∀s ∈ D, C(s) - - - > E(s)
∀s ∈ D, C(s) - - - > ~ E(s) 
∃s ∈ D such that M(s) ∧ C(s) 
Explanation:
D = set of all students
M(s) = s math major
C(s) = s Computer science major
E(s) = s Engineering major
Expressing the following using quantifies variables and predicates :
A.) Every computer science student is an engineering student 
∀s ∈ D, C(s) - - - > E(s) 
b. No computer science students are engineering students 
∀s ∈ D, C(s) - - - > ~ E(s) 
c. Some computer science students are also math majors
∃s ∈ D such that M(s) ∧ C(s) 
∃s = Existential Domain
∀s = universal
∧ = connective and
~ = not
∈ = belongs to