How exactly do i work this out?

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?

What is the slope of any line parallel to the line 8x+9y=3 in the standard (x,y) coordinate plane?

Henry's butcher shop uses an electronic scale that measures to 1/100 of a pound. which is the most accurate measurement based on the limitations of the scale that might be found on a package of meat sold by henry?