Can you help me my son does not understand this home Work

To determine how long it will take the submarine to reach the lab from the surface of the ocean, we need to know how far it is from the surface of the ocean to the lab. Since this is not given, let us present the distance as D.

The submarine travels at 100ft/min

He also travels a distance of Dft

Then the ratio below is correct:

1/100 = x/D

x = D/100

Where x is the time we want to find.

If you have omitted the distance D by mistake, all you need to do is divide it by 100 to get the time you are looking for.