Physics Problem

I have this problem Im doing and i didnt copy all the parts I just jumped to the answer >.> I need to solve for t.

20+0.5vt-16t^2=0

I have here in my notebook that the answer is  t= 92.4/v
but i have no idea how it got there, exam is in 3 hours Help

look up how to solve a quadratic equation, because that is what you have.  You can use a formula called the quadratic formula which will yield two answers, one of which likely is not useful because it is negative and you don't want a negative time.  If At^2 + Bt + C = 0 was your equation, then A = -16, B = 0.5, and C = 20.  You feed those three values into the formula to get solutions.  You could also graph the equation and see where the graph crosses the x (or t) axis.

You can also read up on completing the square