After looking at the questions in the text, I realized that there are a few equations you might need that you may or may not have encountered yet. The main equation that is needed seems to be the quadratic equation.
Whenever you have some form of an equation that resembles the top equation, you can solve for your unknown using the second formula. a, b, and c represent some numerical coefficient. You will be left with two possible values of x; verify which x makes sense (example: negative time makes no sense so is an invalid number). In the context of our questions, we can use the formulae about to solve for t.