Answer:
Step-by-step explanation:
David uses 1 table spoon of sugar for every 1.25 cups of water to prepare lemonade.
Therefore, Number of table spoons of sugar required (S) ∝ Cups of water required (w)
⇒ S ∝ w
⇒ S = kw
⇒ k = 
⇒ k =
= 0.8
So the formula to calculate the amount of water will be,
S = 0.8w
⇒ w = 
where k = proportionality constant
Now we can complete the table with the help of the formula.
Sugar (tbsp) Water (cups)
1 1.25
7 8.75
3 3.75
5 6.25