Math Arguments

SAT Number theory

This is an actual SAT question, from later in a section so it is one that a lot of test-takers got wrong because it was a hard question, was worded strangely, had too many undefined letters, or was near the end of a section and the test-takers simply ran out of time.

What are some of the difficulties you think most students would have with it? What are some things we could do to rewrite the question so it's more clear?