which method is easier to use? substitution method or elimination method?

It depends on the values gives, for example If you have two equations like
a+2d=5
a+6d=12
In this case it would be more straightforward to use the elimination method because you can just subtract, since the a's would immediately cancel out.

In all cases though I prefer the elimination method. I find it takes less time.

depends. i find elimination easier.

There is not a specific answer to this.
It depends upon the question and indeed upon the person doing the question.

It really depends on the problem, but all things being equal i find elimination easier.