How do you use the variable time in a kinetic equation?

For kinetic equations, I just found out that you can't solve for time alone by plugging in all the other variables. I'm confused as to what time is for then in a kinetic equation. It seems like time has no function if you can't solve for t ? And WHY can't you solve for t? (I tried to but the answers come out wrong). I get that time should be solved using a speed over distance equation (thanks to billruss), but it seems to me that I should get hte same answer for time using a kinetic equation. I don't know - I'm just very confused about physics right now.