Easiest way is to use your movie's framerate...i.e. 30fps
each scene has a stop at frame 1.....a stop at frame 9000 (30x30fps 30 secs)
your timer is placed at frame 1 your question placed at frame 1
your countdown placed at frame 30,60,90,120 etc etc
your countdown removed at frame 31,61,91,121 etc etc
you have a button for question 1 it says goto and play scene..frame 2
now your question will appear...every 30 frames along the timer will show 1 less second.....when it gets to frame 9000 you can have an action to send to a fail page...or back to the question buttons...
tldr....thats the easiest way to think it out, if you need it scripted then search for 'timer' or 'screensaver' to get further ideas