Fair market value in taxes?

So my brother purchased a house in 2012 and I went to live with him in 2012 on that property. After 2017 my brother moved to another state and in 2017 my brother gifted his house to my mom and my mom gifted it to me the same year. I recently sold the home and I do not know if I am suppose to register for taxes the price my brother payed for the home in 2012 or when my mom passed it to me on the fair market value in 2017. If it is 2017 FMV do I just take zillow FMV chart of what it was and print it out and submit that with my taxes this year or just submit the FMV price of what it would have been in 2017 online without the paper to show it?

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Your cost basis in the home is his purchase price + the cost to buy + any improvements made by him or mom + any gift taxes he and/or mom paid on the gift tax form 709 they each should have filed reporting the gift over the allowed max for those tax years.