I'm just going to write out the steps for an equation I use at a restaurant and I hope you in the community wouldn't mind answering by showing how the equation should be written properly.
I use this math process, or equation when dividing the quantity of cashew milk out for bottling at a restaurant I work at.
BEGIN: I have some total amount of cashew milk over 8 quarts, (though the quantity is always unknown and the equation party solves this variable part of the process). I split the total cashew milk in half for drink 1. The rest of the cashew milk goes to making 3 equal quantities of drinks 2, 3, and 4. ALTHOUGH, this half of the cashew milk is not split into 3rds because drink 4 is a coffee drink. This coffee drink is 2 parts cashew milk and 1 part coffee. Though this drink with coffee is not 100% cashew milk the end goal is to make the same quantity of this drink as I do drinks 2 and 3, which are all cashew milk by volume.
The math gets heaviest here
To figure out how much cashew milk the coffee drink (drink 4) needs I add 1 + 1 for the drinks with 100% cashew milk in them each plus 0.666 for the coffee drink which is 2/3rds cashew milk. I divide 0.666 by 2.666 and get 0.249. As a percent this rounds to 25% so I take 25% of the half of the total cashew milk. 0.333 divided by 2.666 tells me how much coffee I need. I divide 1 by 2.666 to get the percentages of drinks 2 and 3 from the total, which is 0.375 or 37.5% of the half of the total.
I hope that is clear and would just like to know if there is a proper equation form this can be written in.
I find this very difficult to follow here's what I understand. We have an initial volume $M$ of cashew milk. $M/2$ is set aside for drink $1$, and the remaining $M/2$ is used for drinks $2,3,4$. Drinks $2$ and $3$ take an equal volume $V$ of the milk, but drink $4$ takes $\frac23V$ so that $$V+V+\frac23V=\frac M2$$ or $$V=\frac{3M}{16}$$ The amount of coffee required $C$ is $$\frac V3=\frac{M}{16}$$
Does this answer your questions?