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Đáp án:

`↓↓↓`

Giải thích các bước giải:

`A = (2015 + 2016 + 2017)/(2014 + 2015 + 2016 + 2017 + 2018) . 2020`

`-> A = (2014 + 1 + 2014 + 2 + 2014 + 3)/(2014 + 2014 + 1 + 2014 + 2 + 2014 + 3 + 2014 + 4) . 2020`

`-> A = ( (2014 + 2014 + 2014) + (1 + 2 + 3) )/( (2014 + 2014 + 2014 + 2014 + 2014) + (1 + 2 + 3 + 4) ) . 2020`

`-> A = (2014 . 3 + 6)/(2014 . 5 + 10) . 2020`

`-> A = (3 . (2014 + 2) )/(5 . (2014 + 2) ) . 2020`

`-> A = 3/5 . 2020`

`-> A = 6060/5`