What is the value of n so that the expression x^2+11x+n is a perfect square trinomial?

I’m still confused on how to work the percentages

The pair of coordinates that do not represent the point( 5,150’) is a. (5,-210) b. (5,210) c. (-5,330) d. (-5,-30)

David leaves his house to go to school. he walks 200 meters west and 300 meters north. how far is david from his original starting point?