Atype is typically makes an error on one out of every 21 documents they complete if the typist can complete 120 documents an hour how many errors does he make in three and a half hours

Can someone me out here and the tell me the greatest common factor

In right ∆abc shown below, the midpoint of hypotenuse ac is located at d and segment bd is drawn. if ab = 12 and bc = 16, then explain why bd = 10. hint: consider what you know about the diagonals of a rectangle.

I'm a polygon i have no parallel lines i am formed 3 line segments i have one right angle two of my angles are angles what am i