That question asks what you would bring to a friend's birthday party. You can answer accordingly, does it have to be in English or Spanish?
Por. Para would be used to say that something was made *for* someone.
parallelogram law of vector addition states that if two vectors act along two adjacent sides of a parallelogram both pointing away from the common points, then the resultant is represented by the diagonal of the parallelogram passing through the same common point.
