To this mixture we're adding ounces of water, so that the new mix has a total volume of ounces and matches the composition of the coffee Lily likes. This means it would consist of
ounces of water
ounces of cocoa (same amount of cocoa as before because pure water is being added)
Solve for :
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Just to confirm: the new mixture consists of
ounces of water
ounces of cocoa
giving a total volume of ounces of coffee, and , as required.