Would it be unreasonable to mark this a NAA: https://math.stackexchange.com/a/3614418/29335
I mean, a solution should not be something that is l-i-t-e-r-a-l-l-y applicable to any proposition of the form "Show A implies B". At least, not in this case. Proving the contrapositive offers nothing more than proving the original statement by, say, contradiction, so the suggestion seems empty, to me. A comment, at best. It is not really even a *hint*.