Can't tell the difference between permutation and combination In an exam, a student has to answer 6 out of 8 questions. How many ways can she answer the 6 questions if 
a) there are no restrictions?
b) The first 3 questions are compulsory?
c) she must answer at least 3 of the first  4 questions?
I am confused. Why is this question combination? I thought it is supposed to be a permutation. The 6 questions that the student is supposed to answer are specific. For example, each question is unique on its own. That is my understanding, but its wrong ._. Can anyone correct my logic?

Consider a finite set $A$, so $\exists$ natural $n$: $|A|=n$, there  are no problems thinking $A$ as $\{1,2,...,n\}$. Let's define permutations and combinations:
Permutations of ${A}:=\big\{ f: \{1,2,...,n\} \rightarrow \{1,2,...,n\}$ bijective$\big\}$
Combinations of $k$ elements extract form $A:=\big\{ S \subseteq A: |S|=k\big\}$ 
Very importatnt facts: 


*

*You can think a permutation of $A$ as a $n$-tuple with all different entries because of a bijection (e.g: let $A=\{1,2,3\}$. $(2,1,3)$ represent the permutation $f: f(1)=2$ etc). In $n$-tuples order matter.

*Combinations are sets (subset of $A$)! When you consider a set order doesn't matter.

