To find the velocity, we need to differentiate the position equation with respect to time.

Given: x = -50 + 5t

When t = 0,
x = -50 + 5(0) = -50

When t = 5 minutes (or 5/60 = 1/12 hours),
x = -50 + 5(1/12) = -50 + 5/12 = -50 + 0.4167 = -49.5833

Now, to find the velocity (v), we differentiate the position equation with respect to time:

dx/dt = d/dt (-50 + 5t)
dx/dt = 5

Therefore, the velocity at x = 80m is 5 m/s.