What was the change in the balance of software solutions between 2017 and 2018?
{"Balance, December 31, 2017": {"Software Solutions": 2134.7, "Data and Analytics": 172.1, "Corporate and Other": "$\u2014", "Total": 2306.8}, "HeavyWater and Ernst acquisitions (Note 3)": {"Software Solutions": 22.9, "Data and Analytics": "\u2014", "Corporate and Other": "\u2014", "Total": 22.9}, "Balance, December 31, 2018": {"Software Solutions": 2157.6, "Data and Analytics": 172.1, "Corporate and Other": "\u2014", "Total": 2329.7}, "Compass Analytics acquisition (Note 3)": {"Software Solutions": 31.7, "Data and Analytics": "\u2014", "Corporate and Other": "\u2014", "Total": 31.7}, "Balance, December 31, 2019": {"Software Solutions": 2189.3, "Data and Analytics": 172.1, "Corporate and Other": "$\u2014", "Total": 2361.4}}
balance_2018 = df["Balance, December 31, 2018"]["Software Solutions"]
balance_2017 = df["Balance, December 31, 2017"]["Software Solutions"]
answer = balance_2018 - balance_2017