Inequalities
Let's call m to the number of minutes Vanessa runs the garden hose to add more water to the pond.
We know the hose can add 48 gallons of water in 2 minutes. Therefore, it can add 24 gallons per minute (dividing by 2 both quantities).
Now we know the hose can add 24 gallons of water per minute, we can also know it can add 24m gallons of water in m minutes.
For example, if m=10 minutes pass, the hose adds 24*10=240 gallons of water
Obviously, the maximum time Vanessa can run the garden hose will depend on the pond capacity.
Since the pond can hold no more than 256 gallons, we create inequality:
24m < 256