How do you compute the value of each item sold as part of a group of other items? Let's say there's a sign outside a grocery store that reads: "3 Apples, 1 Orange, 5 Bananas: $7.50".
You come back the following day, and it reads: "5 Apples, 2 Pears, 1 Banana, 7 Pineapples: $12.50".
And so on. Don't waste your time trying to solve this particular problem as I just made up the numbers, but the idea is that the store only sells items in groups, and the individual price of each single item is never exposed to the customer. The store sells a finite set of items (let's say 30 or so different kinds of fruits), but they can be sold in a large number of configurations.
Given enough daily trips to the store, can we solve for the value of each individual item? In other words, what value does the store put on 1 apple?
This is not from school or a textbook; I play a popular mobile game called Raid Shadow Legends, and each week they have a selection of "Limited Special Offers". To give you an idea, here are today's offers:
Bonus Skill Pack: Legendary Tome x 7, Gems x 2,750, Epic Tome x 7, Silver x 2,750K : $99.99
Mini Mix Pack: Ancient Shard x 3, 100% XP Boost x 5, Rank 4 Chicken x 6, Clan Boss Key x 3, Energy Potion x 13, Arena Token x 10, Brew x 45, 2, Silver x 2,500K : $24.99
Great Deal Mix Pack: Epic Tome x 7, Legendary Tome x 2, Energy x 950, Blue Brew x 15, Red Brew x 15, Green Brew x 15, Purple Brew x 15, Silver x 950K : $34.99.
That's generally what they look like. There are people on Youtube punching numbers into spreadsheets they've cooked up to try to estimate if these are good deals or not, but it seems to involve a lot of chin-stroking and estimating and "I would say"-ing, etc.
It's probable that the company putting these packages together is in fact tweaking things day-to-day so coming up with hard numbers may be impossible, but I would expect certain trends to emerge upon analysis over time. How can we break this down with math?
 A: You can hope that each item has a given price and that the price of a group of items is the sum of the prices of the items in a group.  This will give you a system of linear equations.  If you collect as many data points as there are different items you are likely to be able to find a unique solution.  Spreadsheets can automate this for you.  If you collect rather more data points than there are different items, you can do a least squares fit to find an average price for all the items.  When a new package comes out, you can see how its total matches with the prices you have.
You can also use game experience to put your own value on the items.  Maybe you have discovered that a Blue Brew doesn't do much useful but a Red Brew is twice as good and a Green Brew ten times as good.  If you truly believe those numbers, you can eliminate some of the items in favor of others before you do your pricing and you will need fewer data points.  It could be that the Blue Brews become much more valuable later for reasons that are not yet clear, so your view of the values may change.
I have not played the game at all, but I would predict that the price of items will generally decrease with time.  This means people doing this analysis will find the newly published groups to be a good deal and may spend more money.  It may be compensated by making the items less valuable in-game, by making the game more difficult and introducing new, higher priced items to deal with the higher difficulty.  After all, their objective is to get you to buy packages.
A: Regarding the fruit example, you can solve for the cost of each individual fruit:

*

*if you have as many independent equations as you do different kinds of fruit, and

*the cost of the fruit doesn't change from day to day.

Let's say you have apples and bananas. The first day you see "one banana and three apples for $\$0.25$" and the next day you have "two bananas and two apples for $\$0.30$." You have two independent equations with two unknowns (the price of the banana and the price of the apple) and therefore can solve the problem (bananas are ten cents each and apples are five cents each).
(If the second day we had instead "two bananas and six apples for $\$0.50$", then we couldn't solve the problem yet, because the equations aren't independent. All you know is that if you buy twice as much, you pay twice as much. These equations are dependent.)
If you have thirty fruits, then you need thirty independent equations to solve for the prices of all of them.
Now to get to your game question, it's not likely that the prices of the individual items stay the same for the deals, so it's not like you can solve for the prices of the individual items the same way.
If you have some other measure of value, then you can add all of the individual prices to see what the discounts for the packs are, but that's about it.
Hope this helps. Welcome to Math.SE.
