Changing the subject of a formula
I'm new to this forum and I was hoping someone could please help me with something.
I'm trying to learn algebra and am working through a book doing all the practice exercises. There is one question in particular under the subject of changing the subject of a formula that I don't know how the answer was derived.
The question is:
Make y the subject of Attachment 19703
The answer is Attachment 19705
I can't figure out how they've come to that answer and there is no explanation in the book. Can anyone help please?