I teach secondary and postsecondary math courses. The term "literal equation" was used in Texas where I taught for 17 years. The Algebra 1 state standard A.12E says that students are expected to "solve mathematic and scientific formulas, and other literal equations, for a specified variable." I also taught college undergrad courses in Texas, including College Algebra, and I don't recall ever seeing the the term used there, but I used it in class because my students were familiar with it. Now I teach in Oregon, and the term is not a part of this state's standards from what I can tell.