Answer:
f=15
Step-by-step explanation:
f/6=2.5
f=2.5*6
f=15
9 stacks of cards and 4 cards left over because when you divide 85 by 9 you get 9.4. So you'd multiply just 9 to get 81 and 4 cards leftover
The standard form: Ax + By = C.
We have:

<h3>Answer: x - 4y = 8</h3>