What is the increase / (decrease) in Adjusted EBITDA from 2018 to 2019?
{"Revenue": {"2019": 2072.0, "2018": 2168.0, "%Chg": -4.0}, "Operating expenses": {"2019": 1932.0, "2018": 1972.0, "%Chg": -2.0}, "Adjusted EBITDA": {"2019": 140.0, "2018": 196.0, "%Chg": -29.0}, "Adjusted EBITDA margin": {"2019": 6.8, "2018": 9.0, "%Chg": -2.2}, "Capital expenditures": {"2019": 102.0, "2018": 90.0, "%Chg": 13.0}}
adjusted_ebitda_2019 = df["Adjusted EBITDA"]["2019"]
adjusted_ebitda_2018 = df["Adjusted EBITDA"]["2018"]
answer = adjusted_ebitda_2019 - adjusted_ebitda_2018