For part (a) set up two equations of motion  one for the elevator and one for the bolt  and set them equal to each other. If the initial height of bolt off the grounbd is h, and measuring time from when the bolt stars to fall:
Bolt position: y_b = h  1/2 g t^2
Elevator position: y_e = y0  vt, where y0 = the elevator's position when the bolt started its fall. Since that is 5 seconds after it passes the bolt, and it's moving at 5 m/s, you know that y0 = h vt = h25 m. So:
y_e = h  25 m  5m/s x t
Set y_b = y_e and solve for t (notice that the h terms cancel out).
For part (b) you need to calculate how far the bolt falls in the time you calculated in part (a).
