The parametric equations that show her position are x(t)=8t and y(t)=-16t^2+100.
When t=2.5 8(2.5)=20 and -16(2.5)^2+100=0.
8(2.5) gives the answer to the second answer of her being away 20 feet from the cliff. The second equation gives the answer to the first answer and she reaches the ground at 2.5 seconds.
