Question

How does a "for every" statement show a ratio comparison? (Example of a for every statement: There a 5 strawberries for every 6 apples)

Answer 1

For every means for example if there is going to be one apple there will always have to be 2 orananges so every time one apple adds there will be always 2 oranges

Answer 2

If you think of the "for every" as a : then it will make sense. So, replace the "for every" with a :.
So:
There are 5 strawberries for every 6 apples 
Turns into
strawberries:apples = 5:6