One of the shortfalls of the Goal Seek tool is that you can only change one input cell at a time to affect the answer. If you want to have Excel change more input cells you need to use the Solver tool.
So in the example below there is a simple coffee shop and all we want to know is what is the maximum total revenue (red circle) we can achieve by changing how many cups of each coffee type we sell. If you run this as is, Excel would just try a bigger and bigger number. So when you run something like this, you need to have some constraints. Note in cells G12 to G14 we are told that we have a maxinum number of each type of coffee we can sell on a day. Excel needs to know this in order to 'guess' the appropriate number of cups to sell.
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