Coming back again to "Remove odd hashes" task, it is not clear either what the additional parameters :a and :b are passed in for ? Should we check the sum of only :a keys, only :b keys, or :a and :b key in the provided hash?

I think the task 'remove any hash whose two keys sum to an odd number.' should be rephrased to be clearer. For me, we can't sum the keys (:a, :b in this case) but sooner their values which are integers.