Ba, bd and bf are angle bisector of adf find m

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;

Describe the 2 algebraic methods you can use to find the zeros of the function f(t)=-16t^2+400.

Askateboard ramp is in the shape of a right triangle what is the height of the ramp