Here is a simple explanation of the basics. A copy of this will cost about as much as 1 lesson;
Amazon.com: edly's music theory for practical people - third edition: Books
I second this suggestion! I've been working through this book for two weeks and I already have a very practical working knowledge of scales, intervals, and triads. It's feels a little ridiculous carrying it around and reading it in public because it looks like it was written for an elementary school chorus class, but each concept is explained so well and builds so cleanly on the concept before it, that I think it's well worth anyone's time.
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