What is the percentage change of net cash provided by operating activities between fiscal year 2017 to 2018?
{"": {"2019": "", "2018": "(U.S. $ in thousands)", "2017": ""}, "Net cash provided by operating activities": {"2019": 466342, "2018": 311456, "2017": 199381}, "Net cash used in by investing activities": {"2019": -604198, "2018": -51696, "2017": -224573}, "Net cash (used in) provided by financing activities": {"2019": -3187, "2018": 906789, "2017": 9438}, "Effect of exchange rate changes on cash and cash equivalents": {"2019": -855, "2018": -630, "2017": 465}, "Net (decrease) increase in cash and cash equivalents": {"2019": -141898, "2018": 1165919, "2017": -15289}}
net_cash_2018 = df["Net cash provided by operating activities"]["2018"]
net_cash_2017 = df["Net cash provided by operating activities"]["2017"]
answer = (net_cash_2018 - net_cash_2017) / net_cash_2017 * 100.0