Kelsey read 75% of the 40 books she bought. how many books has kelsey completed

In triangle abc segment de is parallel to the side ac . (the endpoints of segment de lie on the sides ab and bc respectively). find de, if ac=20cm, ab=17cm, and bd=11.9cm;

Use the elimination method to solve the system of equations -x+5y=-4 and 4x+3y=16

Select the best attribute for the angle pair formed by two parallel lines intersected by a transversal.