Explanation:
Start with what you know and list your knowns and unknowns
F = ma
F= 3N
m = 6kg
a =?
3N = 6kg x a
solve for a
3N / 6kg = a
1. A vector
is a unit vector if its magnitude is 1. Given

and
are unit vectors, while
is not, since

2. Given some vector
, you can get the unit vector in the same direction as
If

then the unit vectors in the direction of
and
, respectively, are

3.

