Which notation is the proper way to write vector quantities?

[GreenPrint]

What' the proper way to write vector notation? For a force...
(10 N)i + (5 N)j + (6 N)k
or are the brackets not standard and I can just go like this when I can indicate the superscript arrow above the unit vectors
10 Ni + 5 Nj + 6 Nk
I'm not exactly sure and was hoping someone could tell which is correct
thanks

 

[GreenPrint]

i wasn't sure weather or not to place this in the advanced physics section sorry if I should of

 

[ufarad]

My physics textbook had, for instance, a velocity written as $5.0 \hat{i} + 3.6 \hat{j} - 8.4 \hat{z}$ m/s. That is, numbers followed by unit vector letters with hats on them and after all three, the unit.