Mixtures are a somewhat rare problem type on the GMAT. When GMAT studiers see them, they're often bamboozled.
However, mixtures are actually pretty straightforward. They're simply a combination of two equations: weight and amount of substance. I explain more in the video, and show the process on two sample questions.
If you want a bunch more lessons and fully-explained practice problems for every type of GMAT quant topics, get my book the GMAT Quant Bible: https://gum.co/SXUSJW