How do I calculate the amount of an element after heating a compound?

Here is the question that I am given and I'm not sure how to go about getting the answer: "Upon strong heating, Cu2(CO3)(OH)2 or Cu3(CO3)2(OH)2 decomposes to leave CuO(s) in the heating crucible. Upon heating of 1.103 g of sample, 0.793 g remains. Calculate the %Cu in the sample."