This question from the Free Practice tests generated lots of questions. It's something that's not exactly taught in traditional math classes. Instead, it's closely related to ratios taught in beginning algebra. The big difference is that, in algebra, you're setting up a formula. With this, you only have to add the parts, divide the volume, and then multiply for each part.
Remember to keep the ratio in order, then:
1. Add all parts together
2. Divide up total volume by total number of parts
3. Multiply volume per/part X individual ingredient parts.
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