What is the change in additions and adjustments between 2017 and 2018?
{"Beginning balance, January 1": {"2019": 2429, "2018": 7478, "2017": 3532}, "Additions and adjustments": {"2019": 1074, "2018": 1691, "2017": 7680}, "Write-offs": {"2019": -2128, "2018": -6740, "2017": -3734}, "Ending balance, December 31": {"2019": 1375, "2018": 2429, "2017": 7478}}
additions_and_adjustments_2018 = df["Additions and adjustments"]["2018"]
additions_and_adjustments_2017 = df["Additions and adjustments"]["2017"]
answer = ( additions_and_adjustments_2018 - additions_and_adjustments_2017 )