The answer is
840 gallonsTo get this answer, it is easiest if we set it up as a fraction.
We can write this to represent how much we know Clydesdale drinks:
This represents that they drink 120 gallons for every 4 days.
Now for what we're looking for:

The x represents how how many days
Now we just compare fractions:

=

If we look at the denominators, 4 is multiplied by 7 to get 28, so to find our missing numerator, we multiply 120 by 7, which gives us our answer:
840So,

=

Hope this helped!! :)