While by no means logically incorrect, it feels inelegant to setup a problem using variables A and B in the first paragraph and solve for X and Y in the second (compounded with the implicit X==B, and Y==A).
1. How to Write Mathematics — Paul Halmos
2. Mathematical Writing — Donald Knuth, Tracy Larrabee, and Paul Roberts
3. Handbook of Writing for the Mathematical Sciences — Nicholas J. Higham
4. Writing Mathematics Well — Steven Gill Williamson
My complaint stems more to the general observation that readability is prized in math and programming but not emphasized in traditional education curriculum to the degree it is in writing.
Bad style is seldomly commented on in our profession.