We can represent these value using variables. Let’s call cups of flour F, and cups of milk M.
So, for every cup of milk we have 4 cups of flour.
We can also wright this as M= 4F
When we have one M (cup of milk) it must be equal to 4F (cups of flour),
For every one M we have 4F.
We can replace M and F with X and Y. They still mean the same thing, we just often see expressions written with X and Y in math.
So,
y=4x
