If the submarine moved from the water surface at a speed of (-20) m per minute, it means it is moving downwards.
To find the distance the submarine is from the water surface at the end of 7 minutes, we can use the formula:
Distance = Initial position + (Speed x Time)
Since the water surface level is considered as zero, the initial position is 0. The speed is given as (-20) m per minute, and the time is 7 minutes.
Distance = 0 + (-20) m/min x 7 min
Distance = 0 - 140 m
Distance = -140 m
Therefore, at the end of 7 minutes, the submarine is 140 meters below the water surface.