Does it handle strings and symbols for keys?

Did you change your code, or did the method mysteriously start working? I'm still getting NoMethodErrors for Array#any? and Array#all?

think about the different ways each method should respond based on the state of the class. Since we know the calc should execute once given three inputs...you can setup your methods to behave differently

Yeah, some techniques take a while to get under the skin. However, reading and trying to understand other peoples solutions will likely put you a step further, so keep going (And I see you are closing quite a few katas :)).