Răspuns:
a = 2013
Explicație pas cu pas:
2020 - 2019:{2018 - 2017:[2016 - 2015:(2014 - a)]} = 1
2020 - 1 = 2019:{2018 - 2017:[2016 - 2015:(2014 - a)]}
2019 = 2019:{2018 - 2017:[2016 - 2015:(2014 - a)]}
2018 - 2017:[2016 - 2015:(2014 - a)] = 2019:2019
2018 - 2017:[2016 - 2015:(2014 - a)] = 1
2018 - 1 = 2017:[2016 - 2015:(2014 - a)]
2017 = 2017:[2016 - 2015:(2014 - a)]
2016 - 2015:(2014 - a) = 2017:2017
2016 - 2015:(2014 - a) = 1
2016 - 1 = 2015:(2014 - a)
2015 = 2015:(2014 - a)
2014 - a = 2015:2015
2014 - a = 1
2014 - 1 = a
a = 2013
