Answer: Hi!
So first, I'm going to convert "350 below ground level" to -350, as this is what "below ground level" represents.
Now, we should find the total distance traveled. Take the absolute value of -350 (350) and add it to 10, the metres above ground level. This is 360.
We already know the rate of travel; 6m/min. All we have to do now is divide the total distance (360) by the rate of travel (6)!
360 ÷ 6 = 60
So, it took 60 minutes, or one hour, for the elevator to travel down the shaft!
Hope this helps!