In the given question, the final target is to get to the equation where "s" is expressed in terms of "t". Now if we look at the problem very closely, we get numerous information's that can used to determine the answer that is asked in the question.
Amount of drinks contained in each small bottles = s liters
Amount of drinks contained in each large bottle = t
Since the quantity of juice in a large bottle is 1 litre more than that present in the small bottle, Then
Amount of drinks contained in each large bottle = (s + 1) liters
Now we can write the equation as
s + 1 = t
s = t - 1
So this is the final equation that has been asked to be found in the question.