<p>Is this question missing information, or what...?</p>
<p>If a, b, c, and f are four nonzero numbers, then all of the following proportions are equivalent EXCEPT</p>
<p>(A) a/f = b/c
(B) f/c = b/a
(C) c/a = f/b
(D) a/c = b/f
(E) af/bc = 1/1</p>
<p>looks like A is the odd one out hint :)</p>
<p>Yes, I have got that much from the answers…</p>
<p>OH! WAIT! Okay, lightning just struck. I got this.</p>
<p>It is A because if you cross multiply all of the solutions, the only one that is not af=bc or some similar variation, is choice A, which is ac=bf. I hope that makes sense!</p>