(20t-4t^2)/5=24/25
5(20t-4t^2)=24
100t-20t^2=24
25t-5t^2-6=0
5t^2-25t+6=0
t^2-5t+6/5=0
(t-5/2)^2-25/4+6/5=0
(t-5/2)^2=101/20
t-5/2=±√505/10
t=5/2±√505/10
(20t-4t^2)/5=24/25
5(20t-4t^2)=24
100t-20t^2=24
25t-5t^2-6=0
5t^2-25t+6=0
t^2-5t+6/5=0
(t-5/2)^2-25/4+6/5=0
(t-5/2)^2=101/20
t-5/2=±√505/10
t=5/2±√505/10