@Michael_B, can confirm this is in Kaplan chapter 6 of Physics.
Checking through, ohms isn’t explicitly defined as a unit but V = IR is given as an equation and the unit make-up can be deduced using it. Just wanted to mention this bc it’s one of those ones that might be in a grey zone as to whether to tag. But since it can at least be deduced, we can add on the tag
That’s what I was intending to reflect from; equation 6.5 in which it gives V = IR and discusses all the relative units. Though it is good to point out that, being a deduction, it’s not a straight line to that factoid from the book material. That’s good to know.