How do I calculate the order of a reaction given slope?
As mentioned, you don't want a direct answer so I am just going to ask you some question to think about, that hopefully help in getting you to the answer. Please reply in the comments whenever something is unclear to you!

You're expecting first order in both reactants, so if you would write down the reaction rate equation, what does that look like?

With the equation you should have one unknown only: $k$ (or two that make up $k$: $k_0$ and one other, which?, if you are interested in the temperature effect as well).

Now calculate $k$ for each reaction separately. Are they the same? Do you expect them to be? If they're not, should you average them?