There are 7 sides available.
The fundamental counting principal tells us to find the total number of combinations of independent items, multiply the number of choices from each one (choices x choices x....)
This means that drink x sides x sandwiches = 560. We know there are 16 sandwiches and 5 drinks. Let S be the number of sides:
15(6)(S) = 560
80S = 560
Divide both sides by 80:
80S = 560/80
S = 7
The same constant value(s)
If you turn the ratio 1:3 into a fraction it would be 1 over 3 I hope this helps
The second one is the correct answer