What was the change in the net cash provided by operating activities from 2018 to 2019?
{"Net cash provided by operating activities": {"2019": 35746, "2018": 34339}, "Less Capital expenditures (including capitalized software)": {"2019": 17939, "2018": 16658}, "Free cash flow": {"2019": 17807, "2018": 17681}}
net_cash_2019 = df["Net cash provided by operating activities"]["2019"]
net_cash_2018 = df["Net cash provided by operating activities"]["2018"]
answer = net_cash_2019 - net_cash_2018