Complex sentence: In the 2010s there was three Friday the 13ths in 2012 and 2015, and two in 2013,2017,2018,2019, and 2020.
Split into simpler sentences: In the 2010s there were three Friday the 13ths in 2012 and 2015, and two in 2013. There will also be two 2017,2018,2019, and 2020.